TEGUCIGALPA - Honduran troops and police clashed on Tuesday with hundreds of supporters of ousted President Manuel Zelaya outside Brazil's embassy where he took refuge after slipping back into the country in a bid to return to power.

Supporters of ousted Honduras President Manuel Zelaya run amidst tear gas fired by police, near the Brazilian embassy in Tegucigalpa September 22, 2009. Honduran police dispersed hundreds of supporters on Tuesday outside the Brazilian embassy where ousted President Manuel Zelaya took refuge after sneaking back into the country in a bid to return to power. (REUTERS/Oswaldo Rivas) Police fired tear gas at the demonstrators, who threw rocks back at security forces. A Reuters photographer said at least two gas canisters landed inside the embassy compound.

Soldiers patrolled streets around the embassy and enforced an all-day curfew called by Honduras' de facto government to dampen the protests in support of the leftist Zelaya, who was toppled in a June 28 coup.

Zelaya ended almost three months of exile by sneaking back into Honduras on Monday. He sought refuge at the Brazilian embassy to avoid being arrested, and accused security forces on Tuesday of preparing an attack.

"The embassy is surrounded by police and the military ... I foresee bigger acts of aggression and violence, that they could be capable of even invading the Brazilian embassy," Zelaya said in an interview with Venezuelan broadcaster Telesur.

The military and police kept a strong presence outside the embassy and a police spokesman said all the protesters had been dispersed. Tegucigalpa's main hospital treated 20 people injured in the scuffle, some with broken legs and arms and head wounds but none in serious condition.

Brazilian President Luiz Inacio Lula da Silva said his government would guarantee Zelaya's right to seek refuge in the embassy, ignoring off the de facto government's demands that Brazil either give Zelaya asylum and take him out of the country or hand him over for arrest.

Honduras' de facto leader Roberto Micheletti took power after Zelaya was toppled and forced into exile on June 28. Despite economic sanctions imposed by the U.S. government and the European Union, Micheletti has repeatedly refused to back down and insisted Zelaya would be arrested if he returned to Honduras.

Micheletti's government appeared to be winning the battle of wills and was betting that the international pressure would ease after a new president is elected in November and takes power in January.

But Zelaya's surprise return has put new pressure on his rivals with the threat of street protests.

"I'm calling on all the population to come to Tegucigalpa because we are in the final offensive for the restitution of the presidency," Zelaya told a local radio station late on Monday.

CALLS FOR NEGOTIATIONS

The United States, the European Union and the Organization of American States have called for negotiations and a return to democratic rule in the Central American country.

With Zelaya mobilizing his supporters and the de facto government imposing a curfew, the EU also told all sides on Tuesday to "refrain from any action that might increase tension and violence".

"I insist that the courts are waiting so he can present himself there and pay for the crimes he committed," Micheletti said on Monday night.

Jose Miguel Insulza, head of the Organization of American States, canceled a planned visit to Honduras because airports were shut, and urged both sides to negotiate a settlement.

Soldiers toppled Zelaya at gunpoint and sent him into exile in his pajamas after the Supreme Court ordered his arrest, saying he had broken the law by pushing for constitutional reforms that critics say were an attempt to change presidential term limits and extend his rule.

He denied the allegations and says he had no intention of staying in power beyond the end of his term. Zelaya had upset Honduras' business groups, opposition leaders and a large chunk of his own party by developing a close alliance with Venezuela's socialist president, Hugo Chavez.

(Additional reporting by Arshad Mohammed in New York; Writing by Alistair Bell; Editing by Kieran Murray and Jackie Frank)