Students and opponents of the Venezuelan government have called a new rally for Wednesday to mark a month of protests in Caracas, as the death toll from demo-related violence reached 21.

Students throwing rocks and homemade firebombs clashed late Tuesday with police who tried to disperse them with tear gas and water cannon. No injuries were immediately reported.

Panama's president told Venezuela on Friday that its decision to break off diplomatic ties should not be an excuse to renege on its massive debt to the Central American nation.

President Ricardo Martinelli's warning came a day after Venezuela ordered the expulsion of Panama's ambassador and three other diplomats in a worsening dispute stemming from protests against the Caracas government.

Venezuelans will march again on Saturday against the country's chronic food shortage, one of the major grievances in a wave of protests shadowing President Nicolas Maduro's government.

At least 20 people have now died in Venezuela since protests first erupted a month ago, giving Maduro his biggest test since succeeding late leader Hugo Chavez almost a year ago.

In the face of violent protests roiling Venezuela, many of Latin America's leaders have backed the government of President Nicolas Maduro, some have stayed mum and only a few have complained.

The region's few voices of dissent have been conservative leaders -- Panama's Ricardo Martinelli so angered Maduro that the leftist Venezuelan president broke off ties with Panama City -- but by and large, those voices have been muted.

The Venezuelan government ordered Panama's ambassador and three other diplomats at the mission to leave the country within 48 hours, a Panamanian official said Thursday, a day after Caracas broke ties with Panama City.

"We received a note from the foreign ministry of Venezuela that was delivered to our embassy in which it declared four diplomats working in our embassy as 'persona non grata,'" Panama's Deputy Foreign Minister Mayra Arosemena told reporters.

A police officer and a civilian died Thursday during clashes in the Venezuelan capital Caracas, bringing to 20 the toll from a month of anti-government demonstrations in the divided country.

The member of the National Guard succumbed in hospital to a gun shot wound to the chest while a man on a motorbike also died, State Attorney General Luisa Ortega Diaz told local television.

President Nicolas Maduro called Thursday for a meeting of South American leaders on the turmoil in Venezuela after more than a month of anti-government street protests.

Maduro made the request to visiting Suriname President Desi Bouterse, the current head of the Union of South American Nations (Unasur).

Venezuela marked the first anniversary of Hugo Chavez's death Wednesday with a blend of solemn ceremonies, clashes and a break in relations with Panama over protests dogging his successor's presidency.

President Nicolas Maduro led a military parade with tanks, fighter jets and elite troops before a ceremony next to his mentor's marble tomb in former barracks that sit atop a Caracas slum.

The House of Representatives on Tuesday voiced near-unanimous condemnation of Venezuela's government and its "inexcusable" deadly crackdown on opposition leaders and protesters.

The chamber passed a resolution blasting President Nicolas Maduro's forces for their oppressive tactics in some of the most serious South American unrest in years.

Thousands of flag-waving protesters flooded the streets of Venezuela's capital Tuesday to keep the pressure on the government on the eve of commemorations marking the anniversary of Hugo Chavez's death.

Led by students, marchers dressed in white proceeded peacefully as they streamed through middle-class neighborhoods of Caracas toward Petare, a sprawling slum on the city's eastern edge.