(Adds quote on withdraw, context)
BEIRUT, Aug 7 (Reuters) - The Lebanese army was assessing on Thursday whether militants who seized a town near the Syrian border had withdrawn overnight as part of an agreement made between Sunni Muslim clerics and the government, a security source said.
The source said there was no fighting on Thursday morning in the border town of Arsal but that the army had killed 14 Islamist militants during fighting on Wednesday evening, responding to a breach of the new extended 24-hour ceasefire.
He said three policemen, members of the Internal Security Forces, who were captured earlier this week by the gunmen were found in a hospital on the southern edges of Arsal.
"The army is investigating whether the gunmen have all withdrawn from Arsal in accordance with the agreement between the government and the Muslim Clerics Association," he said on condition of anonymity. He added that the army has not yet entered Arsal.
Arsal is the first major incursion into Lebanon by hardline Sunni militants - leading players in Sunni-Shi'ite violence unfolding across the Levant - which threatens the stability of Lebanon by inflaming its own sectarian tensions.
The battle in Arsal, a predominantly Sunni Muslim town, has triggered unrest in other parts of Lebanon. A bomb exploded near an army patrol in the northern city of Tripoli, also predominantly Sunni, killing one person and wounding 11 on Wednesday evening, security sources said. (Reporting by Tom Perry; Writing by Oliver Holmes; Editing by Toby Chopra)