Heavy rain has been battering Gulf states, causing flash floods that have killed 20 people and disrupted flights at the world's second-busiest airport.

Dubai Airport said it was facing "very challenging conditions" on Wednesday. It advised passengers not to turn up as runways were inundated with water.

Further north, a man died when his car was caught in flash floods.

In Oman, rescuers found the body of a girl in Saham, bringing the death toll in the country to 19 since Sunday.

Authorities also warned that more thunderstorms, heavy rain and strong winds were forecast, with many low-lying areas still under water.

The United Arab Emirates, Oman's northern neighbour, experienced on Tuesday its largest rainfall event since records began 75 years ago.

The National Centre of Meteorology announced that 254.8mm (9.7in) had fallen on Khatm al-Shakla, in the emirate of al-Ain, over less than 24 hours.

The country averages 140-200 mm of rainfall per year, while Dubai typically receives only 97mm. The monthly average for April is only about 8mm.

Footage from the centre of Dubai showed dozens of submerged vehicles on a flooded part of Sheikh Zayed Road, as well as long traffic jams elsewhere on the 12-lane highway.

British tourist Caroline Seubert, 29, from Leyland in Lancashire, told the BBC that she and her husband were currently stranded at a shopping centre in Dubai.

Ms Seubert, who is 22 weeks pregnant, said they had headed to Dubai Mall on Tuesday morning because they had booked tickets for its aquarium and had not been warned by their hotel that it could be unsafe because of the storm.

"The mall was flooded, ceilings were collapsing, the place shut at 7.30pm. We were told to leave, but the metro was shut and the taxis were not running or picking up in the area," she said. "We were stranded, had to sleep in the mall lobby overnight."

They managed to catch a taxi in the morning, but it could not reach their hotel and dropped them off at another mall on the way, she said.

"We still can't get taxis to agree to take us to our hotel 15 minutes down the road, and our hotel refused to put their usual mall shuttle bus on in order to help people," she said.

Another British citizen who lives in Dubai, Ross Moore, told the BBC the storm was "an incredible sight to see".

"I have never seen anything like it in the UAE and I've been here since 2017," said the 35-year-old. "The thunder and lightning was incredible, the noise was something I'll never forget."

He said his home was in an area on higher ground, so a little water came in but they have managed with sandbags and towels against the door.

"I went out with my son yesterday afternoon, just within our community, and everything was flooded, all the roads. Last night trucks came in and collected all the water."

No deaths were reported in Dubai, but an elderly man was killed when his vehicle was swept away in a flash flood in Ras al-Khaimah.

Although the rain had eased by Tuesday evening, Dubai International Airport warned on Wednesday morning that "recovery will take some time".

The intense storm that began on Tuesday morning and continued through most of the day forced the airport to suspend operations for 25 minutes, divert several inbound planes and cancel a number of inbound and outbound flights.

Videos posted on social media showed aircraft ploughing through several inches of water that completely covered the airport's apron and taxiways.

"We are currently experiencing significant disruption due to the weather and are continuously working with our emergency response teams and service partners to restore normal operations as quickly as possible," it said on X, formerly Twitter.

Emirates, one of the UAE's two flag carriers and the world's largest international airline, meanwhile told customers that check-in had been suspended at the airport for all flights until midnight (20:00 GMT).

FlyDubai, Emirates' low-cost sister airline, said some outbound flights would operate from one terminal after 20:00.

Its chief executive, Paul Griffiths, told local radio station Dubai Eye: "In living memory, I don't think anyone has ever seen conditions like it."

Software engineer Kanish Kumar Deb Barman, who is stuck at the airport on his way home to India, told Reuters: "There are hundreds and thousands of other passengers just like me in this airport who have been waiting for 10 hours, 16 hours, some even for 24 to 30 hours."

The UAE's National Emergency Crisis Management Authority did issue a warning before the storm telling people to stay at home. The government also told its employees to work from home and private schools were also advised to carry out remote learning.

In Oman, more than 1,400 people have been evacuated to shelters. Schools and government offices have been closed as a precaution.

On Sunday, 10 schoolchildren aged between 10 and 15 and an adult were killed when their bus was swamped by floodwater as it attempted to drive through a wadi in the al-Mudhaibi area of Sharqiya province, about 115km (70 miles) south of the capital, Muscat.

Three other children and the driver were rescued. Two of them were reportedly airlifted to safety after being swept 600m (1,970ft) from the bus.

The sultanate's council of ministers said it was "filled with grief" over the deaths and sent their condolences to the victims' families.

Precipitation is scarce in Oman. Annual average rainfall ranges from 150 to 300mm in the north, with most falling in pre- and post-monsoon storms.

The heavy rain also hit Saudi Arabia and Bahrain, where videos showed cars stranded in flooded roads.

There are reports that recent "cloud-seeding" in the skies above the UAE might have caused the record-breaking event - but BBC Weather meteorologist Matt Taylor says the storm had already been predicted by forecast models. Cloud-seeding, the practice of altering clouds to make rain, has been going on in the United Arab Emirates for more than 10 years.

The rainfall was caused by an area of low pressure centred to the south of the Arabian Peninsula, which pulled warm, moisture-laden air in to the region from the Indian Ocean south of Oman, he adds.

Many factors contribute to flooding, but a warming atmosphere caused by climate change makes extreme rainfall more likely.

The world has already warmed by about 1.1C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to emissions.