Fighting continues to intensify in Yemen as the internationally recognised government forces push a military offensive against the Iran-backed Houthis, an armed group also known as Ansar Allah, which controls part of the country.

Speaking at the United Nations Security Council on Friday, the UN Special Envoy to Yemen, Hans Grundberg, said the country has effectively slid back into “full-scale war”.

Government forces are particularly looking to retake the important Bab al-Mandeb strait at the entrance to the Red Sea, a vital trading chokepoint that has become an important alternative to the Strait of Hormuz, where Iranian attacks have all but halted shipping.

At least 46 civilians have been killed and more than 130 others injured since August, many of them children, according to the United Nations.

More than 200,000 people have been displaced since fighting escalated in September, the UN’s migration agency (IOM), said.

Fierce battles across several fronts have prompted concerns from rights groups that Yemen has essentially returned to civil war after the relative quiet brought by a 2022 ceasefire that followed a lengthy civil war which first erupted in 2014.

Amid the US-Iran war, Yemen’s worst fighting in years threatens to destabilise the region further, experts say. Here’s what we know:

What’s the latest on the ground?

Saudi-backed Yemeni forces are advancing on the Houthis in a bid to recapture areas around the Bab al-Mandeb, a critical trade route for global shipping into and out of the Red Sea. Riyadh has increasingly relied on it for oil exports amid the US-Iran war, which has closed the Strait of Hormuz.

On Sunday, the Yemeni government announced the start of the operation “Dawn of Yemen”, which aims to retake all remaining Houthi-held territory, including the capital, Sanaa.

On Saturday, it said it had conducted more than 2,750 precision strikes during military operations over the previous 24 hours, resulting in the “neutralisation” of more than 1,400 Houthi fighters.

The spokesperson for the armed forces, Colonel Majid al-Nuzaili, said in a statement carried by Saba news agency that the operations also targeted high-value military assets deep within Houthi-held territory.

He added that ground forces “successfully” breached Houthi defences, recaptured operationally significant positions, secured their field gains and continued to advance the offensive according to operational plans.

The Bab al-Mandeb strait emerged as yet another front in the US-Israel war on Iran when the Houthis declared a blockade on ships linked to Saudi Arabia in July.

While the Houthis said that was in retaliation for ongoing Saudi blockades on Yemen, analysts viewed the move as calculated to provide more leverage for Iran amid on-and-off negotiations with the US – a close ally of Riyadh.

Battles are now raging around the strategic southern cities of Mocha and Dubhab, which are on the Red Sea coast and strategically important for control of Bab al-Mandeb. The Houthis, who have controlled Sanaa and parts of northwestern Yemen since 2014, seized the area in September, effectively taking control of the strait, although both sides currently claim control of the shipping lanes.

The Houthis, who have developed sophisticated weapons systems, including ballistic missiles, have also targeted Saudi Arabia with missile and drone attacks. On Friday, Saudi Arabia’s aviation authorities said three Saudi citizens, including a pilot, had been killed and several others wounded in Houthi strikes on the international airport in Riyadh – the first such deaths in the kingdom since fighting resumed. Several airlines suspended flights.

The coalition forces also heavily bombarded Sanaa, on Friday, with several injuries reported, including a child. Both sides are also fighting to control Taiz.

What led to the original civil war?

Civil war began in 2014 when the Houthis took control of Sanaa and imposed their own government in the capital. The seizure came amid dissatisfaction with the ruling government and following a revolution three years earlier.

A coalition of armed forces and local armed groups backed by Saudi Arabia launched military operations and restored the internationally recognised government in Aden. Fighting resulted in the deaths of between 150,000 and 227,000 people, while millions were displaced.

While the Houthis controlled much of the north, the Yemeni government controlled the southern regions.

A UN-brokered truce in 2022 saw a lull in fighting and allowed aid to reach the deprived population, which has faced famine since 2016.

In 2023, the Houthis, who form part of Iran’s “Axis of Resistance” alliance of proxy armed groups, began disrupting shipping in the Red Sea in response to Israel’s genocidal war on the Gaza Strip. In March this year, the Houthis fired missiles at Israel amid the war on Iran, officially entering the US-Israel war with Iran which began in February.

Tensions escalated when the group declared a naval blockade of Saudi ports and shipping passing through the Bab al-Mandeb strait in July, shattering the relative calm in the country since 2022. It followed the announcement with a lightning ground offensive on Mocha, pushing back Yemeni coalition forces from the strategic port city.

In September, the group’s forces again swept through and seized territory along the western coast and the Bab al-Mandeb strait, including the strategically located Mayyun Island in the strait.

On October 4, Rashad al-Alimi, leader of the Yemeni government’s Presidential Leadership Council (PLC), announced a military offensive to “restore state authority”.

Is this a return to war?

Analysts say the scale of fighting means Yemen has fallen back into civil war as both sides come under scrutiny for targeting civilians.

As the UN Special Envoy to Yemen, Hans Grundberg, declared that the country has effectively slid back into “full-scale war”, civilians, including women and children, are the ones bearing the “brunt of escalating violence”.

The envoy stressed the need for the UNSC to support urgent mediation once more, although analysts have pointed out that recent gains by Yemeni government forces could mean they are more determined to push through the ongoing offensive, rather than agree to a settlement.

But “unless war is to become Yemen’s permanent reality, the time to consider political strategies is now”, Grundberg warned.

Reporting from Sanaa, Al Jazeera’s Yousef Mawry, said: “It is beginning to resemble the 2015 Saudi-led coalition war on Yemen, when Sanaa and various other provinces were attacked relentlessly around the clock.”

A number of sites in Sanaa have been targeted, he said, including Sanaa International Airport. Several industrial facilities, including a chips factory in the north and a sponge factory in the south, have also been hit.

At least four telecommunications infrastructure sites have been struck in the capital and throughout areas controlled by the Houthi movement. Mount Attan in Sanaa was also hit by 10 air raids.

Mawry reported that, according to Saudi coalition officials, strikes have destroyed 136 military targets in areas under Houthi control, including military sites, launch pads and radars belonging to the Houthi group.

“Meanwhile, the Houthis accuse Saudi Arabia of targeting public infrastructure and telecommunications facilities, warning that the campaign risks plunging the country back into a humanitarian crisis similar to the one experienced from 2015 to 2022,” Mawry said.

Will the United States take action in Yemen?

The US, which has previously indicated that it does not want to get involved in the Yemen conflict, nevertheless on Friday called on the Houthis to stop attacks on Saudi Arabia and Yemen’s internationally recognised government, while demanding that Iran end its support for the group.

Speaking at a UN Security Council meeting on Yemen, Jeff Bartos, the US ambassador to the UN for Management and Reform, said Washington was “gravely concerned” by the Houthis’ recent escalation, including attacks on civilian infrastructure and airports.

“The pattern remains unmistakable. The Houthis act as instruments of Tehran to threaten freedom of navigation, undermine regional stability, and terrorise innocent civilians,” Bartos said.

“We demand that the Houthis cease their attacks against the legitimate governments of Yemen and Saudi Arabia and we demand that Iran cease all support to the Houthis,” he added.