Making their first contact with fighters of Tehrik-e-Taliban chief Baitullah Mehsud in a new offensive in Pakistan's South Waziristan region, army troops killed 50 militants in an aerial and artillery bombardment.
Fresh fierce clashes were also reported on Saturday between security forces and rebels in Bajaur and Mohmand tribal areas close to the border with Afghanistan.
Pakistani fighter jets and attack helicopters pounded militant hideouts in South Waziristan killing 50 Taliban fighters during the past 24 hours, military officials were quoted as saying by the Dawn news channel.
These were the first known casualties among Mehsud's fighters in South Waziristan, where the Al-Qaida chief Osama bin Laden and his outfit's other top commanders and Taliban leaders are believed to be holed up.
The strikes were conducted after ground forces supported by tanks moved into areas dominated by the Mehsud tribe. Columns of troops were seen moving from Wana, the main town in South Waziristan Agency, to Madijan, an area adjoining the Mehsud territory.
However, officials said the action did not herald the start of a full-scale operation on Waziristan, where the army has completed its deployment and is occupying strategic positions.
Washington is strongly backing Pakistan's move to launch a military campaign in Waziristan and has conveyed to Islamabad that it will back up the operations by providing intelligence and surveillance.
Helicopter gunships pounded the Mehsud-dominated areas of Kund Serai, Sarwakai and Wara. Two seminaries, a militant training camp and three houses occupied by the Taliban were reportedly destroyed in the assault.
Troops dug trenches on hilltops in Madijan and deployed artillery. An official was quoted by Dawn newspaper as saying that the ground forces would secure the Jandola-Wana road, a key supply route that passes through Mehsud territory, before launching an offensive against Mehsud and his fighters.
Reports said Mehsud's fighters had blocked the Jandola-Wana road with rocks, creating hurdles for the movement of troops. The ground forces plan to encircle Mehsud and his men so that they cannot flee to other areas.
"A full-scale operation is still not underway," officials reported by television channels said. They said the action on Saturday was sort of an advance foray to soften targets before hitting them hard.
A growing number of people have been fleeing South Waziristan because of the planned military offensive. In Mohmand Agency, three militants and a security personnel were killed today when rebels attacked a check post at Ambar. The militants fired rockets at the check post, killing a security personnel. Three militants were killed in retaliatory action by the security forces.
In the restive Bajaur tribal region, security forces killed at least 15 militants in retaliatory strikes on Friday after the Taliban ambushed a military convoy in Chaharmang area. Two soldiers were killed and several others injured in the ambush.
Five more militants were killed in Chaharmang area on Friday when security forces shelled Taliban positions. A military operation was launched in Chaharmang last week.
The Pakistan Army said earlier this week that the government had ordered it to launch an operation against local Taliban chief Mehsud and his network in South Waziristan. Defence Minister Chaudhry Ahmed Mukhtar has said Mehsud would be hit as soon as he is located.
Reports have said the Pakistan Army is coordinating with Afghan and NATO forces across the border for the offensive in South Waziristan.
Meanwhile, sectarian clashes between Shias and Sunnis have flared up again in the Kurram tribal region. One person was killed and six more injured in clashes between members of the rival groups on Saturday.
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