We are very concerned by reports that Father Ly was arrested in Hue

US embassy spokesman

Thadeus Nguyen Van Ly, an outspoken critic of Vietnam's human rights record, was detained on Thursday for "spreading propaganda against the government".

A US embassy spokesman said: "The ambassador and other US officials have raised our strong concerns with the Vietnam Government and urged that Father Ly be returned to his church residence."

In March, Father Ly urged the Americans not to ratify a trade pact until human rights in Vietnam improve.

Shortly afterwards he was placed under house arrest and denounced in the state-run media as a "traitor" for urging the US to link improved trade to guarantees of religious freedom.

Buddhist sentences

Reports from Vietnam on Friday said that two members of a dissident Buddhist group had been sentenced to up to 12 years in jail on charges of disturbing public peace.

Assistant Secretary of State James Kelly: Currently visiting Vietnam

Truong Van Duc, 58, was sentenced to 12 years in jail, and Ho Van Trong, 76, to four years at their trial last Friday

The police said the two men had participated in a rally last December in the southern An Giang province, during which they had encouraged participants to attack the police.

Vietnam's Communist government forbids religious activity by unapproved groups.

Strained ties

The developments coincide with a visit to Vietnam by US Assistant Secretary of State James Kelly, the first senior official of the new American administration to go there.

He was expected to meet the Vietnamese Foreign Minister, Nguyen Dy Nien, on Friday.

Relations with the US have deteriorated recently, with Hanoi accusing Washington of interfering in its internal affairs.

The US recently granted asylum to 24 Vietnamese refugees from an army crackdown on unrest in the highlands.

Vietnam has also expressed anger about delays in the US Congress in ratifying the trade pact, which would give the two countries greater access to each other's markets.