A Cambodian military court has convicted opposition lawmaker Cheam Channy and sentenced him to seven years in prison on charges of creating a secret military force. Politicians and human rights groups are calling the trial and verdict an attempt to silence political opposition.

Cheam Channy of the opposition Sam Rainsy Party stood in silence as military court Judge Ney Thol read the verdict in his one-day trial. The judge says the objective of Cheam Channy was to get secret information from the Cambodian armed forces and damage them.

The court also ruled Cheam Channy had created an illegal armed force to oppose the government and undermine Cambodia's national security. Cheam Channy denies the charges. His party says the lawmaker was simply heading the opposition's parliamentary defense committee.

Defense lawyer Mao Sophearith said his client was convicted without substantial evidence and is considering an appeal. Defense witnesses were not permitted to testify at the trial, and defense lawyers were kept from cross-examining prosecution witnesses.

Lao Mong Hay, who heads a court-monitoring program at a local policy institute called the Center for Social Development, says the case against Cheam Channy was an excuse to clamp down on the opposition. He says the judicial proceedings have been faulty from the start, and the defendant should have been tried in a civilian court, not a military court.

"Legally speaking, the prosecution, the detention, the arrest of Cheam Channy violates the due process of law," he said. "And in our law, he should be released and those who have prosecuted him and arrested him and detained him should be punished in our law."

Brad Adams, the Asia Director of the New York-based Human Rights Watch, called the trial a "complete sham" that poses a serious threat to Cambodia's democracy. The opposition and human rights activists have criticized Cambodia's court system in the past for being a political tool of the ruling Cambodian People's Party and its coalition partner, Funcinpec.

Cheam Channy, relatively unknown on the Cambodian political scene until his arrest on February 3, is one of three opposition lawmakers stripped this year of parliamentary immunity to allow for criminal charges.

Opposition leader Sam Rainsy and his deputy Chea Poch fled the country after losing their parliamentary protection in February. They remain in self-imposed exile. The party says dozens of others are hiding inside Cambodia for fear of arrest or harassment.

Prime Minister Hun Sen has accused Sam Rainsy of slandering him with claims that he plotted the assassination of the country's leading union activist, a staunch opposition supporter.

In a letter issued Monday from his exile in France, Sam Rainsy called the charges against Cheam Channy politically motivated. He said the ruling party is using the courts to discredit the opposition before the next general elections in 2008.

The U.S. Embassy in Phnom Penh issued a statement condemning Tuesday's court ruling. It called on the Cambodian parliament to restore the immunity of opposition lawmakers immediately, and urged the court to reassess Cheam Channy's case "so that justice may be served."