The Honduran army has thwarted an attempt by ousted President Manuel Zelaya to land at Tegucigalpa airport Sunday by blocking the runway with military vehicles.
Speaking on the Caracas-based Telesur network from his plane, Mr Zelaya said he would divert the flight to El Salvador.
Honduran soldiers and riot police fired tear gas to disperse thousands of protesters gathered at the airport to await the president's return. Emergency services said at least one person was killed.
Mr Zelaya left Washington on a chartered plane accompanied by UN General Assembly President Miguel D'Escoto.
The caretaker government had earlier said it would not allow Mr Zelaya's aircraft to land in Honduras, and the country's aviation agency said it was directing his plane to El Salvador.
Mr Zelaya, who had been due to leave power in 2010, was bundled out of office by troops and into exile on 28 June in a military coup, after what his critics say was an illegal attempt to lift the limit on the presidential term.
The Organisation of American States has expelled Honduras for ignoring an ultimatum by organisation to reinstate the president.
Nicaragua denies troop movements
The Honduran interim government has accused Nicaragua of moving troops close to the border between the two countries in a dispute over the military coup in Honduras.
However a Nicaraguan army spokesman told Reuters it was "totally false" that groups of Nicaraguan troops were moving near the border.
