Riot police in the Honduran capital Tegucigalpa, have used tear gas and water cannon to disperse students rallying in support of the country's ousted president, Manuel Zelaya.

Up to 400 students gathered in protest near the Autonomous University of Honduras in the city on Wednesday, some of them throwing rocks at police.

At least four people were arrested.

Clashes have erupted more frequently in Tegucigalpa since the country's interim government warned last week it would no longer tolerate street blockades that have snarled traffic on a near-daily basis since the June 28 coup.

Further protests are expected in the coming days with more Zelaya supporters marching to Tegucigalpa from various regions of Honduras, expecting to converge on the capital on August 10.

Adding to the pressure, some 15,000 nurses and other workers at 28 hospitals declared themselves on an indefinite strike, joining public school teachers who have been off the job for weeks.

The OAS wants to see Zelaya return to Honduras ahead of new elections [EPA]

It hopes to persuade the Honduran interim president, Roberto Micheletti, to negotiate with mediators seeking to return the ousted president.

They want Micheletti to accept a Costa Rican plan under which Zelaya would return to power until new elections could be held.

Jose Miguel Insulza, the secretary-general of the OAS, said that the organisation would name a group of up to five foreign ministers of member countries who would travel next week to Honduras.

Zelaya, who was whisked out of Honduras following the coup, has said negotiations last month mediated by Oscar Arias, the Costa Rican president, foundered because of Micheletti's refusal to consider his reinstatement.