Two bombs have exploded in a busy market in the Kenyan capital leaving at least 13 people dead. More than 70 others wounded in the blasts on a minibus in Nairobi's Gikomba Market.

Kenya's National Disaster Operation Centre said the explosions were caused by homemade bombs and that one person had been arrested.

The British governemnt has warned of a "high threat" of terrorism, and similar advice has been issued by the governments of France, Australia and the US.

Holidaymakers are being advised to leave unless there is "an essential reason to remain".

A source claimed there was "an increased threat to Western nationals since Westgate" - a reference to the attack on the Westgate shopping centre in Nairobi last September by the Somali militant group al-Shabaab in which at least 67 people died.

The US cited hotels, nightclubs and shopping centres in Mombasa as possible targets. Kenyan authorities have pledged to beef up security but insisted visitors were safe.

Karanja Kibicho, principal secretary at Kenya's foreign affairs department, said the advisories were "obviously unfriendly acts".

Interior ministry spokesman Mwenda Njoka added "The threats are perpetual, we are at war. But we have not received any specific threat on the hotels".

The latest bombings follow explosions in Nairobi and Mombasa on May 3rd and 4th, which Kenya blames on al-Shabaab. Seven people were killed.

Irish charity 'Concern', who has worked in Kenya since 2002, says all its team there are unharmed.