Witnesses in the Afghan capital Kabul, say at least 12 people were killed Sunday in U.S. led air strikes, following heavy bombing that targeted Taleban frontline positions outside the city. Meanwhile, the family of slain opposition leader Abdul Haq vowed to avenge his execution.

U.S. warplanes pounded targets across Afghanistan, with huge explosions also reported near the southern stronghold of Kandahar and the western city of Jalalabad. In one Kabul neighborhood, witnesses reported seeing family members pull battered bodies out of the rubble following a U.S. strike.

Saturday a stray U.S. bomb hit a village in opposition-controlled territory, killing several people a few kilometers north of the Taleban's frontlines, which have been repeatedly battered in recent days.

Northern Opposition forces have not made significant gains in the area, despite help from U.S. planes in recent days.

In neighboring Pakistan, thousands of heavily armed militants have massed along the border in a bid to cross into Afghanistan to fight for the Taleban. Javed Cheema, a spokesman for Pakistan's Interior Ministry, said officials are trying to turn them back. "We are having a dialogue with them, and hopefully, we think that the better sense will prevail and they will turn back," he said, "but should they remain defiant the Pakistan government will take the appropriate action."

In the border city of Peshawar, Afghan exiles opposed to the Taleban mourned the execution of one of their own, and vowed not to let Abdul Haq's death kill their cause. The legendary ex-commander was captured and executed Friday on charges of spying for the United States after slipping back into Afghanistan. He was seen as a key supporter of a plan to form a broad-based government for Afghanistan.

Meanwhile, Pakistan was the scene of two fatal terrorist attacks. Unidentified gunmen killed at least 18 people after opening fire in a packed Christian church in southeastern Pakistan. President General Pervez Musharraf vowed to track down and punish those responsible, saying the incident bears the mark of trained terrorist groups.

Also, in the southwestern border town of Quetta a bomb blast on a public bus killed three people and left many more injured. No one has claimed responsibility for either attack.

Pakistan has increased security across the country since it announced it's support for the U.S. led fight against terrorism.