A huge fire has broken out at the main international airport in the Kenyan capital, Nairobi.The Kenya Airports Authority (KAA) said Jomo Kenyatta International Airport (JKIA) had been closed and passengers evacuated.Cabinet secretary for transport Michael Kamau said the fire was "very severe" and urged people to stay away from the airport.Images showed flames raging from one of the main buildings.The interior ministry tweeted that an evacuation of the entire airport was under way, with only essential personnel remaining, but said the fire had been contained.There have been no reports of any casualties and the cause of the fire is not clear.Jomo Kenyatta International Airport is an important regional hub for East Africa, with many long-distance flights landing there to connect to countries across the region.Water 'shortage'Dark smoke could be seen billowing into the sky across much of Nairobi, one report said.Shocked would-be passengers stood outside the airport, bags in hand, watching the blaze.The BBC's David Okwembah, who is at the airport, says many ambulances are going to the scene as well as fire engines.He said a junior police officer told the BBC the fire had started at the airport's immigration offices, although this has not been confirmed.Multiple reports say the arrivals and immigration sections have been devastated by the blaze.The BBC's Anne Soy in Nairobi quotes the government as saying fire engines are running dangerously low on water and tankers are being used to ferry water to the airport.Julian Kyula - a passenger on board one of the last planes to land at the airport before flights began to be diverted - said a large cloud of black smoke had been visible from the plane.He told the BBC's Newsday programme that although the plane had landed the passengers were now stranded in the cargo area - at a safe distance from the blaze but unable to leave the airport."Everyone is very calm, the crew is very calm, and we've disembarked from the plane now," he said, adding that passengers had not been given much information."There's a lot less smoke, so it's already looking a lot better than it did earlier this morning," he said.Mutea Iringo, a senior official at the interior and national co-ordination ministry, earlier confirmed "a serious fire" at JKIA, adding: "We are doing everything possible to avert a crisis."Apart from emergency landings, all flights into and out of JKIA have been cancelled... [the] airport has been shut down."Cabinet secretary for transport Mr Kamau urged people not to obstruct the work of the emergency services."They should allow the emergency work to continue and we kindly request even spectators, people who just want to watch, they should just keep off."The KAA said only emergency vehicles were allowed in the area.