Police and soldiers clashed with thousands of protesters outside Honduras' national palace, leaving at least 45 people injured, as world leaders from Barack Obama to Hugo Chavez demanded the return of a president ousted in a military coup.

President Manuel Zelaya said he would seek to return to his country on Thursday and reclaim control of the government.

He said he would accept an offer from the head of the Organisation of American States to accompany him to Honduras.

Across Latin America, leftist leaders pulled their ambassadors from Honduras and Nicaraguan President Daniel Ortega said El Salvador, Nicaragua and Guatemala would cut trade with neighbouring Honduras for at least 48 hours.

Venezuelan President Hugo Chavez called for Hondurans to rise up against those who toppled his ally.

"We're ready to support the rebellion of the Honduran people," Mr Chavez said.

He later vowed to halt Venezuelan oil shipments to Honduras and called for its soldiers to rise up against "that tyrannical, puppet government".

Protests outside the presidential palace grew from hundreds to thousands, and soldiers and police advanced behind riot shields, using tear gas to scatter the protesters.

The demonstrators, many of them choking on the gas, hurled rocks and bottles as they retreated. At least 38 protesters were detained, according to human rights prosecutor Sandra Ponce.

Red Cross paramedic Cristian Vallejo said he had transported 10 protesters to hospitals, most of them with injuries from rubber bullets.

Congresswoman Silvia Allaya said she counted 30 injured at a single Tegucigalpa hospital and a photographer in another area close to the palace saw protesters carrying away another five injured people. It was not clear how they were hurt.

Officers also briefly detained seven journalists, arresting them at their hotel with rifles drawn, loading them in a military vehicle and taking them to an immigration office, where two officials demanded to see their visas. The group was released a short time later.

In Washington, Mr Obama said the United States will "stand on the side of democracy" and work with other nations and international groups to resolve the matter peacefully.

"We believe that the coup was not legal and that President Zelaya remains the democratically elected president there," Mr Obama said.

"It would be a terrible precedent if we start moving backwards into the era in which we are seeing military coups as a means of political transition rather than democratic elections," he added.

"The region has made enormous progress over the last 20 years in establishing democratic traditions. ... We don't want to go back to a dark past."

The Organisation of American States called an emergency meeting for today to consider suspending Honduras under an agreement meant to prevent the sort of coups that for generations made Latin America a tragic spawning ground of military dictatorships.

During a meeting of Latin America leaders in Nicaragua, OAS Secretary-General Jose Miguel Insulza offered to accompany Mr Zelaya back to Honduras and work for reconciliation and the restoration of the democratic order.

Mr Zelaya said he would accept the offer and wanted to make the trip on Thursday, after attending a meeting of the UN General Assembly today to seek support from its 192 member nations.

"I am going to ask you to accompany me, you offered, and I accept your offer," Mr Zelaya said, moments after receiving a standing ovation from the gathered leaders.

Honduras' new government, however, was defiant. Roberto Micheletti, named by Congress to serve out the final seven months of Mr Zelaya's term, vowed to ignore foreign pressure and began naming Cabinet members, including a new minister of defence.

"We respect everybody and we ask only that they respect us and leave us in peace because the country is headed toward free and transparent general elections in November," Mr Micheletti told HRN radio.