Three people, including a Pakistani, were killed in a suspected drone attack that set off a blast and a fire in Abu Dhabi on Monday, officials said, as Yemen's rebels announced military operations in the United Arab Emirates.
Two Indians and a Pakistani died as three petrol tanks exploded near the storage facility of oil giant ADNOC, while a fire ignited in a construction area at Abu Dhabi airport.
Police said "small flying objects" were found at both places, suggesting the sort of deliberate attack that is unheard of in the wealthy UAE, a renowned safe haven in the volatile Middle East.
"Preliminary investigations indicate the detection of small flying objects, possibly belonging to drones, that fell in the two areas and may have caused the explosion and fire," police said in a statement, adding that the incidents were under investigation.
Yemen's Iran-backed Houthi rebels did not claim the attacks. But the Houthis' military spokesperson announced a "military operation" in the UAE, a partner in Yemen's pro-government coalition, in what would be a major escalation in the seven-year war.
Yahya Saree tweeted that the rebels' armed forces had said they would "announce an important military operation in the UAE in the coming hours".
Drone attacks are a hallmark of the Houthis' assaults on Saudi Arabia, the UAE ally which is leading the coalition fighting for Yemen's government in a grinding civil war.
The rebels have previously threatened to target Abu Dhabi and Dubai, the gleaming crown jewels of the UAE which last year opened its first nuclear power plant.
The Houthis' latest statement comes two weeks after they seized a UAE-flagged ship, the Rwabee, off the Yemen coast, and released footage purporting to show military equipment on board.
The UAE said the Rwabee, whose 11 crew are now hostages, was a "civilian cargo vessel" and called the hijacking a "dangerous escalation" in the busy Red Sea shipping route.
The rebels later rejected a UN Security Council demand for the ship's immediate release, saying it was "not carrying... toys for children but weapons for extremists".
Yemen's conflict has been a catastrophe for millions of its citizens who have fled their homes, with many on the brink of famine, in what the UN calls the world's worst humanitarian crisis.
The UAE joined the coalition against the Houthis before announcing a change of tack in 2019.
The pro-government Giants Brigade, backed by the Saudis and UAE, recently delivered a significant blow to the rebels by retaking three districts in Shabwa governorate.
The clashes were part of a surge in violence in the shattered country, where the war is being fought on several fronts.