ISLAMABAD, March 25: An unknown number of Al Qaeda-linked militants may have escaped a Pakistani army siege of tribal villages near the Afghan border, a senior local security official said on Thursday.

"The possibility of some militants managing to escape the area through various routes is not out of the question," a top security official for the Federally Administered Tribal Areas (FATA) told AFP.

"However tight the cordon may be, we cannot put troops shoulder to shoulder and, therefore, the possibility of one or two men slipping through at night cannot be ruled out."

The army had claimed to have trapped up to 500 Al Qaeda suspects and local tribal supporters in a 50 square kilometre cordon around two villages near Wana in South Waziristan tribal district, after launching its largest ever Al Qaeda assault on March 18.

A "high-value target" was said to be among them. The fierceness and number of fighters led some officials to be believe the target they were protecting could be Al Qaeda number two, Ayman al-Zawahiri. However he was never seen. - AFP