People climbed out of windows and hid under desks to escape as security forces fought gun battles with militant fighters.
At least 15 people have died after extremists staged a “co-ordinated” terror attack on a luxury hotel and office complex in Nairobi, Kenya.
A British man and an American woman are among the casualties. Their bodies were identified based on identification documents.
A Foreign Office spokeswoman said: “The situation is ongoing. We are in contact with the Kenyan authorities who are coordinating a response and stand ready to assist as required.”
The US state department confirmed the death of one of their citizens.
Eleven of the other victims are believed to be Kenyan while the nationalities of two others were not clear.
Kenyan officials had claimed that the incident was over and security forces were “mopping up”, but after another explosion and more gunfire were heard, police warned people to stay away.
In a tweet the National Police Service said: “We wish to caution all members of the public including politicians that Dusit Hotel and the area around 14 Riverside Drive is a Crime Scene that is under an active security operation.
“Until it is declared safe, everyone not actively involved in the operation should avoid the area.
The attack had begun on Tuesday when gunmen set off thunderous explosives and shot people at cafe tables and desks – with the Islamic militant group al Shabaab claiming it was behind the attack.
Dozens of people were forced to hide for hours inside the DusitD2 complex as Police and troops searched for the attackers.
There is still no word on what has happened to the gunmen.
The DusitD2 complex includes bars, restaurants, offices and banks and is a popular destination with US, European and Indian expats.
Earlier on at 14 Riverside, Westlands, Nairobi #RiversideAttack pic.twitter.com/JpnAmOudkl
— Africa Uncensored (@AfUncensored) January 15, 2019
Authorities have not said how many attackers were involved, but surveillance footage appeared to show at least four gunmen were involved.
Another piece of footage from inside the hotel showed Kenyan security officers searching the building and scared workers emerging from hiding as gunfire rang out.
Dozens of people were rushed to safety as armed officers went from shop to shop in the complex. Some people held up their hands to show they were unarmed.
— Africa Uncensored (@AfUncensored) January 15, 2019
Kenyan police chief Joseph Boinnet said the “co-ordinated” attack began with a car bombing targeting three vehicles in the I&M Bank car park, and a suicide bombing in a hotel foyer where a number of guests suffered “severe injuries”.
People ran out of the complex and climbed out of windows to escape, while other office workers said they had to leave colleagues behind, hiding under their desks, as the attack began.
Hotel cleaner Enoch Kibet, who escaped by crawling out of a gate in the basement, said: “People were screaming. I couldn’t believe I was alive. The blast was so loud and shook the whole complex.”
It is the second time in six years that al Shabaab has launched a major attack on Nairobi.