(Adds opposition-designated magistrate, details on vigil)
By Andrew Cawthorne and Anggy Polanco
CARACAS, July 24 (Reuters) - Venezuela's opposition plastered election centers with slogans and rallied in honor of dead protesters on Monday in a final week-long push to force President Nicolas Maduro into aborting a controversial congress.
The unpopular leftist leader is pressing ahead with the vote for a Constitutional Assembly on Sunday despite the opposition of most Venezuelans, a crescendo of international criticism, and some dissent within his ruling Socialist Party.
Critics say the assembly, whose election rules appear designed to ensure a majority for Maduro, is intended to institutionalize dictatorship in the South American nation, a member of OPEC.
But Maduro, 54, whose term runs until early 2019, insists it is the only way to empower the people and bring peace after four months of anti-government unrest that has killed more than 100 people and further hammered an imploding economy.
Knots of opposition supporters gathered at various centers where Venezuelans will vote on the assembly to leave messages, chant slogans and wave banners. "It's preferable to die standing than to live on our knees!" said one poster at a Caracas school.
"They want to install a communist state in Venezuela, but we're tired of getting poorer and will stay in the street because we do not want the Constituent Assembly," said lawyer Jeny Caraballo, 41. "The people are saying 'No'!"
The opposition, which has now won majority backing after years in the doldrums during the rule of Maduro's predecessor Hugo Chavez, also held nationwide rallies in the afternoon in honor of protesters slain during the crisis. Fatalities have included opposition and government supporters, bystanders and security officials.
Mourners gathered in Caracas with rosaries, candles and flags but National Guard soldiers on motorbikes interrupted the ceremony by lobbing tear gas at the crowd.
"The National Guard represses us even when we're praying for our fallen ones," opposition lawmaker Delsa Solorzano said on Twitter.
Later on Monday, rights group Penal Forum reported that lawyer Angel Zerpa, one of the new Supreme Court magistrates sworn in by the opposition in defiance of the government, had been charged with treason in a military court. Zerpa, who was first detained on Saturday, has gone on a hunger strike, Penal Forum director Alfredo Romero said.
48-HOUR NATIONAL SHUTDOWN
The Democratic Unity coalition has raised the stakes by calling a two-day national strike for Wednesday and Thursday, after millions participated in a 24-hour shutdown last week.