Two died and several others were injured on Sunday, when army troops clashed with supporters of Honduras' deposed President Manuel Zelaya, Xinhua reported.
"Police are firing live rounds," a photographer with the La Tribuna newspaper told Xinhua by telephone. One young Zelaya supporter died after being shot in the head.
Protesters said a teenage girl was also killed. A police source said clashes took place when demonstrators tried to access the airport landing strips.
The plane carrying Zelaya circled above the main Honduras airport, unable to land as the runway was blocked by soldiers with military vehicles.
Zelaya was forced to land in neighboring Nicaragua and vowed to try again Monday or Tuesday to return to the country.
"Faced with this situation, we have to go on with what we had planned," he told the Telesur news channel from the plane.
Zelaya's supporters took the streets around the airport starting early morning. Witnesses said up to 30,000 people appeared around the airport. Zelaya said on Saturday he would fly to Honduras accompanied by officials from the Organization of American States (OAS) and the presidents of Argentina and Paraguay.
On Sunday afternoon, demonstrators broke a police cordon and entered the airport facilities. Several witnesses told Xinhua that soldiers threw tear gas grenades into the crowd, and demonstrators fought back with sticks and bottles.
Demonstrations both for and against Zelaya have filled the streets of Honduras' main cities since last Sunday, when he was ousted in a military coup.
Honduras was expelled from the OAS on Saturday after the post-coup government failed to comply with a deadline to restore Zelaya.