* Violence triggered by killings on Friday
* Police shoot to disperse gangs
* Hundreds of villages burnt
By Biswajyoti Das
GUWAHATI, India, July 24 (Reuters) - Police shot at a roving mob in India's northeastern state of Assam on Tuesday as security forces struggled to contain ethnic fighting that has killed 22 people and left remote hamlets in flames, forcing tens of thousands from their homes.
Rioting between Bodo tribespeople and Muslim settlers has raged for days. Several people suffered bullet wounds and others were injured in a stampede when police fired to disperse a gang of 400 on Tuesday morning, a senior police official said.
Soldiers and federal paramilitary troops patrolled Bodo tribe-dominated Kokrajhar town and outlying areas on armoured vehicles mounted with machine guns.
Locals said more reinforcements were needed to stop the violence that spread to rural areas and neighbouring districts overnight, with more hamlets along river banks and in the jungle burned by rival mobs. Some 500 villages have been destroyed.
"The security forces were silent spectators when village after village was burnt down," veteran local politician Urkhao Gwra Brahma told Reuters.
"This morning I thought the situation would become normal, but I was wrong. Violence again started. It is really out of control."
Ringed by China, Myanmar, Bangladesh and Bhutan, India's northeast is home to more than 200 ethnic and tribal groups and has been racked by separatist revolts since India's independence from Britain in 1947.
In recent years, Hindu and Christian tribes have vented strong anti-immigrant and anti-Muslim sentiment against Bangladeshi settlers.
The latest violence was sparked on Friday night when unidentified men killed four youths in the isolated Kokrajhar district, police and district officials said. In retaliation, armed Bodos attacked Muslims, suspecting them of being behind the killings.
Hundreds of men armed with spears, clubs and rocks attacked an express train passing through Kokrajhar on Tuesday, injuring several passengers.
Hagrama Mohilary, the leader of the tribal council governing the region, warned that former separatist rebels had joined the violence to protect Bodo villages. He called for the rebels, who are officially observing a ceasefire, to lay down their arms.
Bodo tribes shot at Muslim villages close to the border with Bhutan on Monday night, a senior police officer who asked not to be named told Reuters. He said no casualties had been reported.
Assam's chief minister, Tarun Gogoi, told TV network CNN-IBN that he hoped the situation would be under control within two days. He said some 30,000 villagers have fled their homes and taken shelter in relief camps, but local officials said the numbers were at least twice that.
Tribal leader Mohilary said relief camps were overcrowded and suffering a shortage of food and medicine because roadblocks across the region had stopped supply trucks. (Editing by Nick Macfie)