All six crew members onboard a US military aircraft that crashed in western Iraq were killed, the US military has said.

The KC-135 military refuelling plane crashed in western Iraq on Thursday, in an incident the military said involved another aircraft but was not the result of hostile or friendly fire.

Iraq’s western desert is a vast expanse of largely empty rocky plains but is also where many Iran-aligned Shia militia have bases and has been the site of repeated Israeli and US airstrikes.

Elsewhere, a French soldier was killed in an attack in Iraq’s autonomous Kurdistan region, the French president, Emmanuel Macron, said on Friday. It is the first French military death in the war.

Since the joint US-Israeli offensive in Iran began almost two weeks ago and plunged the Middle East into war, multiple attacks attributed to pro-Iranian factions have targeted the region, where foreign forces are based as part of an international anti-jihadist coalition.

The pro-Iranian Ashab al-Kahf group in Iraq warned on its Telegram page that French interests “in Iraq and the region” would be “under targeting fire” after the arrival of a French aircraft carrier.

The US has moved a large fleet of aircraft into the Middle East to take part in operations against Iran and has deployed specialist search and rescue units to extract the downed plane crew.

In an earlier statement, US Central Command said it had been carrying out rescue efforts after the US KC-135 refuelling aircraft went down. A second aircraft involved in the reported accident landed safely.

It is the fourth US aircraft lost since the US and Israel launched strikes against Iran on 28 February. Three US air force fighter jets were mistakenly shot down by Kuwait air defences. All crew members in those jets ejected safely.

Thirteen US troops have been killed in the conflict, while as many as 150 US troops have been wounded. The death toll in Iran is more than 1,300, according to the country’s UN ambassador.

Both Donald Trump and the defence secretary, Pete Hegseth, have said the war will probably claim more American lives before it ends.

Six of the US service personnel were killed when an Iranian drone struck an operations centre at a civilian port in Kuwait. They were in the Army Reserve and worked in logistics, keeping troops supplied with food and equipment.

A seventh US service member died after being wounded in an attack on the Prince Sultan airbase in Saudi Arabia on 1 March.

On Thursday, Mojtaba Khamenei, Iran’s new supreme leader, vowed in a statement to avenge the Iranian casualties in the conflict, according to a statement read by a presenter on state television.

Khamenei himself was wounded in an Israeli strike in the first moments of the war, according to some Iranian officials and state TV, and his father and other family members were killed.

Iran’s Fars news agency said US and Israeli strikes hit parts of Tehran on Friday, adding that homes shook from the blasts.

The Israeli military said Iran fired a new barrage of missiles towards Israel overnight. Emergency services reported two people were injured in the country’s north.

Israel continued striking Beirut early on Friday as it threatened to expand operations and seize territory in Lebanon if the militant group Hezbollah did not stop its attacks. Hundreds of people have been killed by the Israeli offensive against Hezbollah and around a million displaced.