Intense fighting with mortars and small arms broke out today in and around one of the largest refugee camps on the Thai-Cambodian border, killing and wounding large numbers of people, Western diplomatic sources said.

They blamed feuding between rival factions of the right-wing Khmer Serei guerrillas who run the camp.

Reports reaching Bangkok said shooting began shortly before sunrise and was still heard at 6 p.m. Initial accounts blamed Vietnamese forces deployed a few miles inside Cambodia, but diplomats later said fighting was sparked by an attempt to overthrow Van Saren, commander of the Khmer Serei forces based at Camp 204 near Mak Mouen.

Van Saren's whereabouts were not known. Most of the camp's civilians, numbering about 60,000 according to a recent census by the International Red Cross, fled to Mak Mouen and two other refugee settlements in the area. Diplomats said the Red Cross removed six truckloads of wounded to medical facilities. Many people died en route.

It was the second instance this year of such fighting between rival Cambodian armed groups, who generally claim that Vietnamese troops supporting the Heng Samrin government are their first enemy.

In early January about 100 people were killed or wounded in a gunbattle inside the nearby Camp 007 that appeared to involve two Khmer Serei groups as well as troops loyal to the deposed Khmer Rouge regime.

In recent months U.S. officials have repeatedly expressed concern for the safety of people in camps like 204, located in disputed territory along the frontier. Refugee agencies estimate that perhaps 150,000 people are residents in Khmer Serei camps.

Predicting a general offensive to clear the border, Western officials have most often mentioned Vietnamese forces as a threat to the refugees security. However, the Vietnamese military operation has so far remained low key, directed primarily against the Khmer Rouge zones of control.

Today's violence came shortly after Red Cross officials claimed to have settled their latest dispute with camp commander Van Saren. Last weekend he reportedly pulled his gun on a Red Cross worker who was trying to take from the camp 31 Vietnamese refugees who had made the overland trip across Cambodia. In retaliation, food deliveries to the camp were suspended. aBut later the Red Cross announced it would resume them after Van Saren's personal assurances of security.