By Edward McAllister

DAKAR (Reuters) - Gambian security agents closed three private radio stations near the capital, Banjul, amid an escalating political crisis triggered by President Yahya Jammeh's refusal to accept his election defeat.

Jammeh, who seized power in a 1994 coup, initially conceded defeat to opposition rival Adama Barrow in the Dec. 1 vote, but then called for a fresh poll, drawing condemnation from local opponents and foreign powers.

The veteran leaders' refusal to step down has opened up the possibility of a military intervention by West African forces after the ECOWAS body said it was putting military forces on alert. Jammeh called that a "declaration of war".

Emil Touray, head of the Gambia Press Union, said Teranga FM and Hilltop Radio were closed on Sunday, while an employee at Afri Radio, owned by Gambian phone company Africell, said its headquarters was shut down by four intelligence agents and a police officer on the same day.

A government spokesman initially said he could not confirm the closures and later did not answer his phone. Touray said he had no further details.

It was not immediately clear why the stations were targeted by Jammeh. The authorities may have taken aim at Afri Radio because the station announced details of Barrow's inauguration, planned for Jan. 19, the Afri Radio journalist said.

The media has come under regular attack during Jammeh's 22-year authoritarian rule, rights campaigners say, and he has often tried to control communications in the tiny country of 1.8 million. The internet was cut during election day, as were international phone calls.

Teranga FM, popular for its review of newspapers in the local wolof and mandinka languages, has been closed four times in recent years.

The station's managing director Alagie Ceesay was arrested in July, 2015, and charged with sedition. He was hospitalized twice in early 2016 while still in detention, Amnesty International said, and later fled to neighboring Senegal.

"It is a slap in the face of the country's democratic process," said Touray. "People will not have access to information in this critical period of our history."

Barrow's election victory was seen as a surprising triumph for democracy in Gambia, which gained independence from Britain in 1965 but has since had only two presidents. But the elation seen on the streets of Banjul in the days after Barrow's victory was quickly extinguished by Jammeh's defiant stance.

(Editing by Richard Lough)