KINSHASA, ZAIRE, OCT. 31 -- A defiant opposition courted further clashes with President Mobutu Sese Seko tonight, appointing an opposition "government" to contest a new Mobutu administration due to be sworn in Friday.

Further increasing pressure on Mobutu, the United States condemned recent bomb attacks on Zaire's anti-government press. The statement issued by the U.S. Embassy was its most outspoken criticism of the government since anti-Mobutu violence broke out five weeks ago.

The opposition Sacred Union coalition also called on Belgium and France to increase the number of foreign troops in Zaire. Despite the declining security situation, Belgium is to withdraw its 850 troops Sunday in accord with a demand by Mobutu.

Thousands of Sacred Union's supporters crowded outside the headquarters of opposition leader Etienne Tshisekedi tonight to hear the announcement of the parallel government, led by Tshisekedi. Hundreds of Mobutu's Civil Guards stood nearby in the darkness, which was only broken by flashing blue lights atop armored cars and arc lights from a motorized water cannon.

The opposition statement said the decision to form what is effectively an illegal cabinet had been taken "in consideration of the total lack of authority of the state and the massacres perpetrated by the regime." The appeal for more foreign troops was a response to the "danger of genocide," the statement said.

Last weekend, a bomb destroyed the opposition newspaper Elima's printing press. In all, five similar bomb attacks took place last week. No one was injured.

Today's U.S. statement described the bombings as "deplorable" and carried out by "elements with access to explosives and munitions" -- a clear reference to the army. Last week, Mobutu said he was unable to prevent the spiraling violence, although many people believe he intends to intimidate the opposition into submission.

The U.S. Embassy statement said the attacks were an attempt to silence the opposition, and it pointed out that pro-government newspapers were publishing without intimidation.

The opposition announcement of a new government came as the new administration of Prime Minister Mungul Diaka faced a major crisis. Two newly appointed ministers resigned from the government that he appointed only Wednesday. Mobutu sacked Tshisekedi from the post of prime minister 12 days ago.

Diaka has said that his government to be sworn in Friday balances opinion and regional representation. However, Tshisekedi denied the prime minister's claim that 40 percent of the 27 ministerial posts had gone to members of the Sacred Union. Key posts in the Diaka government, notably the defense portfolio, have been retained by pro-Mobutu appointees.