The death toll from a Kenyan fuel tanker explosion has risen to 122 after another 11 people died of their injuries, officials said on Monday.

Four people who had been airlifted to a hospital in the capital died late Sunday as well as seven others who were being treated at a provincial hospital, they said.

The earlier toll stood at 111.

"Seven patients who were admitted at the Rift Valley Provincial General Hospital did not make it to Monday morning... They had suffered very high degrees of burns," said Hassan Noor Hassan, a provincial commissioner.

Flames engulfed a crowd scooping fuel when a tanker overturned late Saturday near the country's central Molo town. Some witness accounts said the fire may have been started when someone lit a cigarette.

The incident occurred three days after fire razed a supermarket in the capital Nairobi, killing 27.

On Sunday, President Mwai Kibaki declared a week of mourning during which all celebrations will be cancelled and national flags flown at half-mast. Kibakui also cut short his trip to an African Union summit in Addis Ababa.