Tourists travelling to a wildlife safari at Kenya's famous Masai Mara national park are attacked as they travel through Mombasa.11:44am UK,

Thursday 12 December 2013 Kenya police attempt to suppress demonstrators reacting to the killing of an Islamic cleric at Kenya's coastal

city of Mombasa

Mombasa has been the scene of violent protests in recent months

Attackers hurled a grenade at British tourists in the Kenyan port city of Mombasa, but it failed to explode.

Mombasa's police chief Robert Kitur told the AFP news agency: "The grenade was detonated safely by experts.

"We are investigating the incident and looking for the man who threw the grenade at the tourists and fled."

The tourists, who were in a vehicle in the Likoni district, were travelling from the popular Indian Ocean resort of Diani on the way to a wildlife safari at the Masai Mara national park.

Tourism is a key source of foreign currency for Kenya.

The British High Commission in Kenya said it had "heard the reports and was investigating", but gave no further details.

Kenya has seen a wave of grenade attacks since it invaded southern Somalia in October 2011 to try to oust al Qaeda-linked al Shabaab insurgents.

Explosives have been thrown into restaurants in Mombasa and crowded areas in the capital Nairobi, and there has been a string of attacks in the remote northeast region bordering Somalia.

Al Shabaab claimed responsibility for the assault on Nairobi's Westgate mall in September, in which at least 67 people died during a four-day siege.

In September 2011 gunmen killed Briton David Tebbutt and kidnapped his wife Judith. She was held for six months before being freed.

Three weeks later, disabled Frenchwoman Marie Dedieu was kidnapped from her home on Kenya's Manda island and later died in captivity in Somalia.

Mombasa police say they have strengthened security.

Mr Kitur said: "We are appealing to everybody to exercise caution, especially over this festive season, and to share information with security agencies to win the war on terror.

"We have intensified security at tourist hotels and other vital installations to avert terrorism attacks."