WANA, Pakistan (Reuters) -- A U.S. drone aircraft has fired missiles into Pakistan's South Waziristan region, killing 10 militants, officials said, ahead of an expected Pakistani military offensive in the area.
The United States, facing a growing Afghan insurgency, began stepping up drone attacks on militant strongholds in lawless enclaves over the Pakistani side of the border a year ago despite Pakistani complaints.
Three missiles were fired at militant hideouts in an area near the Afghan border controlled by Pakistani Taliban leader and Al-Qaeda ally Baitullah Mehsud, killing 10 militants and wounding seven, two intelligence agency officials said.
"The missiles hit an office of Mufti Noor Wali, who was once in charge of training militants for suicide attacks," one of the officials said.
It was not known if Wali was among the dead, or if any foreign militants had been killed, they said.
The attack came as Pakistani troops stepped up the pressure on Mehsud's strongholds.
They have carried out air strikes by jet fighters in recent weeks to soften up targets before an expected full-scale offensive.
The drone attack also came a day after thousands of U.S. Marines launched an offensive
against the Afghan Taliban in the southern Afghan province of Helmand.
Helmand shares a 200-kilometer desert border with the southwestern Pakistani province of Baluchistan.New Front?
Pakistan officially objects to the strikes by pilotless U.S. aircraft on its soil, saying they violate its sovereignty and undermine efforts to deal with militancy by inflaming public anger and bolstering support for the militants.
After an alarming expansion of militant influence and aggression in northwest Pakistan, the Pakistani Army went on the offensive in the Swat region two months ago.
U.S. officials have welcomed the offensive, after the Taliban's gains raised fears about Pakistan's stability and the safety of its nuclear arsenal.
The military says it is nearing the end of the offensive in Swat, a former tourist valley northwest of Islamabad, although soldiers are encountering pockets of fighters.
But no Taliban leaders have been among the approximately 1,600 militants the army has reported killed. Independent casualty estimates are not available.
The failure to kill or capture Taliban leaders in Swat has led to fears that they could make a comeback if and when the army withdraws.
Trouble is also brewing in another militant stronghold on the Afghan border, North Waziristan.
A militant faction allied with Mehsud ambushed an army convoy there on June 28, killing 16 soldiers.
Analysts say the army is reluctant to open a new front in North Waziristan while it is finishes off in Swat and prepares for South Waziristan, but it would want to hit back in response to the killing of the 16 men.
Helicopter gunships have struck in the area this week and on July 3, jet fighters bombed militants to the west of Miranshah, the main town in North Waziristan, killing five of them, residents and security officials said.