Riot police fire tear gas as Venezuelan opposition protests

Riot cops fired tear gas at protesters in Venezuela on Monday as thousands demonstrated against President Nicolas Maduro's efforts to reform the constitution in a deadly political crisis.

Venezuela's opposition boycotted a meeting on Monday to discuss Maduro's plan for a new popular assembly, preferring to protest in the streets where they were again blocked by security forces firing tear gas.

In familiar scenes from five weeks of unrest, youths with gas masks and makeshift shields faced off with police and National Guard troops in Caracas. This was after hundreds of demonstrators were stopped from reaching government offices, including the education ministry.

Masked protesters responded by hurling rocks and other projectiles in clashes in the capital Caracas, with other violence reported in the western states of Merida and Zulia.

The constituent assembly

Maduro's "constituent assembly" super body opened on Monday. The body has the power to rewrite the constitution and shake up public powers. The opposition has refused to take part in the assembly.

Saying the constituent assembly is a trick to keep Maduro in power, representatives of the opposition Democratic Unity coalition or MUD refused to attend despite an invitation from Education Minister Elias Jaua who is leading the constituent assembly process.

"The doors are open, especially to the spokespeople of the MUD. Dialogue is the way forward," Jaua said.

Opposition congressional speaker Julio Borges rejected the plan as "constitutional fraud." The opposition has called his constitutional move a ploy to resist calls for early elections.

Instead, the opposition is demanding elections to resolve Venezuela's grave political and economic crisis and say Maduro is an autocrat.

They blame Maduro for the economic crisis that has caused food shortages.

Late March, Maduro and the Supreme Court made a surprise attempt at stripping Congress of its legislative powers. The president backed down after facing harsh criticism from foreign leaders and local opposition.

The 54-year-old successor to Hugo Chavez says his foes are seeking a coup with US support.

Since early April, the unrest has killed at least 37 people and left hundreds injured.

Tried by the military

Local rights group Foro Penal or Penal Forum said 1,845 people had been detained since April 1 over the protests, with 591 still behind bars.

Opposition leaders said 200 of those were being processed by military tribunals in Carabobo state.

Military courts have ordered the detention of at least 50 civilians involved in the deadly mass protests against Maduro, the Forum said on Monday.

Alfredo Romero, an attorney with the Penal Forum, said that military hearings involving civilian suspects were known to have been taking place for several days. "So far, 75 people have been brought before Venezuelan military courts. Fifty of those remain in custody," Romero, who is representing the detained civilians, said.

Another forty or so people were expected before judges later Monday, said the lawyer, who denounced what he called an "illegal" bid by a military court to try civilians.

Government officials have not confirmed the arrests or the military processing of civilian suspects.

The 50 people being held are in Guarico state, according to legal expert Luis Betancourt with the forum.

An unpopular president

Private polls indicate Maduro has low approval ratings, with citizens increasingly frustrated about shortages.

"I lost my husband because we could not get hold of medicine. There is no medicine and no food," said Isabel Morales, 68, demonstrating against Maduro in Caracas.

"We cannot go on like this."