Fresh violence has erupted in Venezuela, a day after President Nicolas Maduro called for the constitution to be rewritten.

Armed men clashed on Tuesday with riot police who fired tear gas in Caracas, where hundreds of people blocked streets.

State ombudsman Tarek Saab said on Twitter that masked men threw Molotov cocktails at a building housing a branch of his department in the northern city of Valencia.

A stun grenade reportedly went off in the courtyard of the opposition-controlled National Assembly legislature in Caracas as politicians prepared to hold a debate on how to pressure Maduro.

His plan, announced on Monday, has inflamed the opposition, which is calling for even bigger demonstrations to demand elections. A "mega protest" is planned for Wednesday.

International concern is also rising, with Chile and Argentina among the countries expressing worry.



The United States condemned Maduro's announcement, while Brazil's foreign minister, Aloysio Nunes, branded it a "coup".

"President Nicholas Maduro's proposal for a constituent assembly is a coup d'etat. It is another break with democracy, violating the country's constitution," Nunes said in a statement posted on Facebook.

Nunes said social organisations controlled by Maduro would elect the constituents and draw up a constitution "as he wants it".

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The Venezuelan opposition says that the move further weakens the chances of holding a vote to remove Maduro, whom they blame for an economic crisis that has sparked food shortages and rioting.

Maduro said the process to bring in a new constitution was necessary to fend off what he describes as an attempted foreign-backed "coup" against him.

Washington reiterated its concerns for democracy in Venezuela after Maduro's constitutional announcement.

"We view it as a step backwards," said top state department official Michael Fitzpatrick.

"This process is not, by the initial indications, shaping up to be a genuine effort of national reconciliation, which is really what Venezuela needs now."

The head of the Organization of American States, a regional bloc with its headquarters in Washington, slammed Maduro's move.

"The announced proposal is wrong-headed, unconstitutional and fraudulent," OAS Secretary General Luis Almagro said in a video message.

The past month of protests has shut down many schools and businesses.

Prosecutors said 28 people were killed last month in violence between protesters and police.



Conflicting reports of attacks by government-backed thugs or pro-opposition agitators have sown fear among citizens.

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Lucia Newman, Al Jazeera's Latin America editor, said the demonstration planned for Wednesday may be held at the presidential palace, a move that would put protesters and riot police in direct confrontation.

"This is only the beginning, say government opponents, of what they call a national rebellion to try and force the president out, or at the very least force him to call elections. They aim to increase the pressure on Wednesday with what they call a mega march," said Newman.

Many workers walked to work on Tuesday as protests disrupted transport and metro stations were closed.

"Normally it takes me half an hour to get to work. Today it was two hours," David Ramos, a 58-year-old labourer, told the AFP news agency.

"But you have to protest. There is no food or medicine."

Caracas bus driver Luis Guillermo Perez, 52, kept on supporting Maduro however, as the protests forced him to take detours.

"Why are they blocking everything? They demand freedom and they are denying us freedom of movement," he said. "People are anxious."

The opposition is demanding early elections to replace Maduro.

The president instead said he was invoking his power to create a 500-member "constituent assembly" to rewrite the constitution.

That would cut out other political parties and the opposition-controlled Congress from the process.