Peshawar, Pakistan ? A suicide bomber blew up a packed mosque near the Afghan border at the climax of a Friday prayer service, killing 48 people and wounding scores more in the worst attack to hit Pakistan this year.

Islamic militants were suspected in the blast in the Khyber pass, apparently to avenge recent military operations in the area aimed at protecting the major supply route for NATO and U.S. troops in Afghanistan, authorities said. The route passes in front of the mosque.

Several security officers were killed in the attack, which came hours before President Barack Obama unveiled a revised strategy to “disrupt, defeat and dismantle” the al-Qaida terrorist organization and the Taliban militants operating in Afghanistan and in northwest Pakistan.

Afghan and Pakistani officials praised Obama’s emphasis on civilian aid to their countries, saying it would be an effective way to deal with the growing violence from Taliban and al-Qaida militants.

The bomber sneaked into the mosque and detonated his explosives during the hour-long service, which observant Muslims around the world attend around noon on Fridays, witnesses said.

“As the prayer leader said ‘God is great,’ the bomb went off with a big bang,” said Nadir Shah, a paramilitary soldier who was treated for head wounds in the nearby city of Peshawar. “I felt it was the end of everything. Sometime later when I opened my eyes, I was lying among dead bodies.”

The powerful blast collapsed most of the two-story whitewashed building. Scores of residents and police dug frantically with their hands through the bricks and wood for survivors, but mostly they pulled out bloody, dusty corpses.

With anguished women waiting nearby, police displayed blood-spattered prayer caps and sandals for relatives to examine to see whether they belonged to their loved ones.

Militants in Pakistan and Afghanistan have often killed scores of Pakistani civilians in attacks. Mosques and funerals have been targeted before, but Friday’s blast struck many as plumbing new depths of evil.