A petrol tanker burst into flames Thursday in Nigeria's main city Lagos, killing at least 12 people and leaving several others with severe burns, witnesses and local television said Thursday.

"The accident occurred when the the driver of the petrol tanker lost control and hit a culvet before engulfing in flames," witness Silas Okechukwu told AFP.

He said a 30-passenger bus behind the tanker was also engulfed in flames.

"I counted 12 bodies already burnt in the bus near the burning tanker," he said, adding that a second petrol tanker also caught fire near the scene of Thursday's carnage.

Okechukwu said the accident has caused traffic jam on the Orile road and hundreds of commuters and motorists heading for central Lagos are stranded.

Local television showed video images of the incident -- the latest to hit Lagos, Nigeria's largest commercial centre of some 10 million people, in recent months.

Last October a petrol truck caught fire in the city, killing nine people and leaving several others with severe burns.