Dozens of people were wounded, one of them seriously, on Thursday in clashes between rival factions in the increasingly bitter campaign for next month's referendum on Kenya's draft Constitution, police and witnesses said.

In addition to the injuries, many caused by machete-wielding rioters, a car belonging to a Kenyan lawmaker was set ablaze when then two camps attacked each other in the west of the country, they said.

"A man suffered serious machete injuries on the head and dozens of others were wounded," regional police commander Jonathan Kosgey said from Kakamega, the seat of Western Province about 300km outside Nairobi.

Witnesses told Agence France Presse the violence erupted when supporters of the area MP Bobby Khalwale, who is campaigning for a "yes" vote in the November 21 referendum, attacked "no" supporters who retaliated, sparking a riot.

Khalwale's car was torched during the fracas although police managed to rescue the lawmaker from an angry mob who wanted to attack him, they said.

The clashes were the latest in a spate of violent incidents related to the referendum which have seen both "yes" and "no" rallies attacked by rival camps and disintegrate into chair- and fruit-throwing brawls.

They came as the referendum campaign hits full stride amid rising tension and fears of wider violence over the new Constitution, the first major change to the country's founding document since independence in from Britain in 1963.

The contentious draft has split the government of President Mwai Kibaki, who supports it, and sparked concerns of instability in Kenya, a country that has long had the reputation of being an island of relative calm in volatile East Africa.

Kibaki's foes, led by a Cabinet minister and his political opposition, are urging a "no" vote as the draft retains nearly absolute presidential powers.

The president insists the new Constitution fulfills the aspirations of the Kenyan people and has urged the public to endorse it. - AFP