Far from defusing the crisis, Maduro's announcement on Monday further incensed the center right opposition after a month of protests that have left 28 people dead.

The opposition is demanding early elections to replace the socialist president.

Maduro instead said he was invoking his power to create a 500-member constituent assembly representing a "working class base" and local councils to rewrite the constitution -- cutting out the opposition-controlled Congress.

He said the decree was needed to "block the fascist coup" which he said is threatening the country. Maduro regularly portrays Venezuela as the victim of a US-led capitalist conspiracy.

The opposition rejected the idea because the body drafting the new charter would not be the result of a popular election but rather be composed of workers and farmers from Maduro's traditional support base.

AFP reporters saw streets blocked with makeshift barricades of rubbish and pulled-down trees as people banged pots and blew horns.

"This constituent assembly that Maduro has announced is a manipulation to escape elections," said student Raul Hernandez, 22, one of about 100 people blocking a major avenue in eastern Caracas.

Maduro's announcement to a crowd of supporters on May Day came as security forces sprayed tear gas and water cannon at anti-government demonstrators elsewhere in the capital.