Diplomats in Laos say two European journalists and an American interpreter are to go on trial Friday for their alleged involvement with rebels in the death of a security officer. The three have been held since earlier this month, despite protests from the European Union, human-rights and media-freedom groups.

The three, French photojournalist Vincent Reynaud, Belgian reporter Thierry Falise and American citizen Naw Karl Mua, who is an ethnic Hmong, were arrested June 4 in the northeastern Xieng Kuang province, about 170 kilometers north of the capital of Vientiane.

A spokesman for the Laos Foreign Ministry, Ly Southavilay, says local militia arrested the three men because they were cooperating with what he called, local bandits who killed a security officer. That is a term authorities often use to describe ethnic Hmong rebels. The three were also in breach of their tourist visas by working as journalists in a rebel area off-limit to foreign reporters.

Four Laotian nationals were also arrested, but their fate remains unknown.

Western diplomats, who are seeking to observe the legal proceedings, say the trial will be held 100 kilometers north of the capital in the town of Phonesavanh.

Human-rights groups have voiced concerns about the men's safety. They are being held at Phonthong Prison in the capital, where brutal treatment is reportedly commonplace.

The Paris-based media watchdog, Reporters Without Frontiers, has called on the Laos government to release the three men. Mr. Falise, a former Associated Press reporter in Paris, is a free-lance journalist and photographer based in Bangkok who regularly contributes to the French weekly, L'Express.

Mr. Reynaud is also a Bangkok-based cameraman who contributes to various European Television stations. Naw Karl Mua is a minister in Minnesota who served as the journalist's interpreter.

If convicted of murder, the men could face a sentence of 10 years in prison, or even the death penalty.

Hmong rebels have been fighting in remote regions of Laos since the Communist party took control in 1975. The government denies the existence of the Hmong rebels, who are thought to be behind two deadly attacks this year on buses running along the country's main highway.

The first attack in February claimed 12 lives, two of them European tourists. The second attack in April claimed another 12 lives and injured 30 others.