Myanmar's military-installed government has sentenced more critics to death, bringing the total to 139, and is using capital punishment as a tool to crush opposition, the U.N. high commissioner for human rights said Friday, Ashai news reports. 

High Commissioner Volker Türk said at least seven university students were sentenced to death behind closed doors on Wednesday, and there are reports that as many as four more youth activists were sentenced on Thursday.

“The military continues to hold proceedings in secretive courts in violation of basic principles of fair trial and contrary to core judicial guarantees of independence and impartiality,” Türk said in a statement. “Military courts have consistently failed to uphold any degree of transparency contrary to the most basic due process or fair trial guarantees.”

The military seized power in February last year, ousting the elected government of Aung San Suu Kyi. The army's action was met with widespread peaceful protests that were quashed with lethal force, triggering armed resistance that some U.N. experts have characterized as civil war.

Türk said the military-installed government has arrested nearly 16,500 people for opposing the army takeover, including about 1,700 who have been convicted in secret courts without access to lawyers.

The Students’ Union of Dagon University in Yangon, the country’s largest city, announced Thursday on its Facebook page that seven university students between the ages of 18 and 24 who were arrested on April 21 had been sentenced to death Wednesday by a military court in Yangon’s Insein Prison.

An executive member of the Dagon University Students’ Union told The Associated Press that the seven were accused of links to an urban guerrilla group opposed to military rule and convicted of murder for allegedly taking part in shooting a bank branch manager in April.

In late July, the government hanged four political activists, in the country’s first executions in at least three decades.

The hangings prompted condemnations from Western nations and the Association of Southeast Asian Nations, which has sought to defuse the crisis with a five-point plan that the military government has failed to implement.

“By resorting to use death sentences as a political tool to crush opposition, the military confirms its disdain for the efforts by ASEAN and the international community at large to end violence and create the conditions for a political dialogue to lead Myanmar out of a human rights crisis created by the military,” Türk said.