Donald Trump on Friday blamed Iran for carrying out a drone strike on a cargo ship in the strait of Hormuz, calling it a “foolish violation” of the ceasefire agreement with the US.

One drone damaged the upper deck of the ship but the ship was able to proceed, the US president said. The US shot down three other drones aimed at the ship, he said.

His post on social media did not identify the ship or the time of the strike, but on Thursday the British military said a vessel was hit by a projectile off the coast of Oman.

The development comes during a fragile time for the US and Iran as they work to negotiate a permanent end to the war. Iran has increasingly challenged the region and the US over its control of the strait of Hormuz, even with the current interim deal it reached with the US. last week.

A missile warning in the United Arab Emirates caused by a technical glitch earlier on Friday underscored the ongoing tensions in the region, following the attack on the cargo vessel and Israeli strikes in Lebanon over the past few days.

The mobile phone alert startled many across the city-state of Dubai, the first such alert since the interim ceasefire.

The brief text alert that was sent from the UAE’s interior ministry on Friday was also the first of its kind in Dubai during the Iran war. However, alerts have gone off in the region warning of incoming Iranian missiles and drones following the start of the war on 28 February, when the US and Iran launched their strikes on Iran.

A short time after the alert, the Emiratis said there was a telephone call between the foreign minister, Sheikh Abdullah bin Zayed Al Nahyan, and the Iranian foreign minister, Abbas Araghchi. It quoted Sheikh Abdullah as telling Araghchi that the UAE “emphasized the importance of full commitment” to the interim deal between Iran and the US.

“Serious diplomacy and responsible dialogue are the optimal path for addressing all regional and international crises,” it said.

The US and Iran are still negotiating terms of the interim peace deal, including issues such as getting ships through the key strait and addressing the future of Iran’s stockpile of highly enriched uranium. Under the interim deal, the two sides have 60 days to work out the details.