All flights to and from Kenya from the UK are being suspended from 10pm. The Department for Transport told UK airlines: "The threat level to UK civil aviation interests in Kenya has increased to imminent". It added: "Accordingly, from 10pm tonight UK time, all UK airline operations to and from Kenya must be suspended". British Airways operates daily services between London and Nairobi. A flight was due to leave Heathrow airport at 9.50pm with 170 passengers but BA said it had been cancelled as the plane would have landed in Kenya after the 10pm deadline. However, a flight from Nairobi to Heathrow with 228 people on board will be allowed to land just after 5am Friday as it was departing at 8.25pm UK time, before the suspension took effect. A BA spokesman said: "The safety and security of our customers is always our first priority and will never be compromised. "We remain in close contact with the relevant authorities and will keep the situation under close review." A spokesman for the Association of British Travel Agents (Abta) said tour operators would be offering affected travellers three options - to transfer to a flight at a later time, to transfer to an alternative destination or have a refund. However, Kenya will defy the warning and scheduled flights by its airlines will proceed. Kenyan security minister Chris Murungaru said the British flight suspension was "extreme" and allowed attackers the appearance of a moral victory. Around 1,200 Britons are currently thought to be holidaying in Kenya, including about 100 with Thomson Holidays, which was suspending all Kenyan bookings for the next 10 days. The flight suspension comes after Kenyan security forces were placed on high alert when a senior minister said there was intelligence that al Qaeda members were planning another attack somewhere in east Africa. National security minister Chris Murungaru said security measures had been stepped up around foreign diplomatic missions, particularly the British High Commission and US Embassy. Around 100,000 Britons holiday each year in Kenya, which was the scene of a devastating car-bomb attack on an Israeli-owned hotel in Mombasa last November. Three bomb-attackers died in that attack and killed 13 others. At the same time, two missiles were fired at an Israeli charter jet but failed to hit their target. Before the grounding of flights, the Foreign Office had issued a warning to tourists to Kenya saying: "The risk of global terrorist activity in Kenya remains high. "Although the vast majority of visitors to Kenya enjoy a trouble-free stay, all visitors to Kenya should take all sensible precautions and be extremely vigilant especially in public places. "Crowds and demonstrations should be avoided. Keep abreast of international and local news." The advice added: "In particular there is a potential threat against Western interests in Nairobi." The British High Commission in Nairobi was closed for four days in December, 2002 following a "specific threat". **PHOTO CAPTION*** A Kenyan listens to a memorial service on the site where a bomb blast destroyed an Israeli-owned hotel in Mombasa, Kenya, November 2002.(AFP/File/Pedro Ugarte)