Updated

The Taliban claimed responsibility for two weekend homicide bombings in the northwestern Swat Valley, saying Monday the blasts were a message to a visiting U.S. envoy that the militants remained strong despite recent Pakistani army gains there.

The attacks -- coupled with another bombing that killed seven elsewhere in the northwest Monday -- showed that the Muslim extremists can still sow violence and fear despite losing Swat to the military and reportedly their top leader to a U.S. missile strike elsewhere near the Afghan border on Aug. 5.

Celebrations by residents returning to Swat for Pakistan's independence day last week were followed by two blasts Saturday and Sunday, the first since the army declared in late July it had regained control of the valley. The first bombing on a security checkpoint killed five people. Two soldiers died in another attack after a cornered militant detonated his explosives.

A Swat Taliban spokesman called The Associated Press from an unidentified location Monday to say the militants timed the attacks to coincide with the visit U.S. envoy Richard Holbrooke, who has been tasked with pressing Islamabad to crackdown on extremists threatening Pakistan and Afghanistan.

The bombings were "a gift to Holbrooke," Muslim Khan said. "The Taliban cannot be eliminated."

Holbrooke, who arrived Friday night, had been scheduled to travel to Mingora, Swat's main city, on Sunday but canceled, citing bad weather.

The envoy met Monday with Pakistani Prime Minister Yousuf Raza Gilani and praised the army's success in Swat and nearby regions, according to a statement from Gilani's office.

The offensive began in April after the Taliban advanced to within 60 miles of the capital, Islamabad.

It was the Pakistan's largest anti-militant operation after years of intermittent peace deals with various factions in areas of the northwest.

Gilani repeated a plea for Washington to supply his government with the same unmanned drones that fired a missile believed to have killed top Pakistani Taliban leader Baitullah Mehsud in his stronghold of South Waziristan earlier this month. The U.S. is believed to have already rebuffed that idea.

On Monday, police said they arrested a close aide to Mehsud who was being treated in a private hospital in Islamabad.

Militant commander Qari Saifullah, who also has links to Al Qaeda terrorists, told police he had been wounded in an American missile strike in South Waziristan, said two police officials, who spoke on condition of anonymity because they were not authorized to release the information. It was unclear if it was the same strike believed to have killed Mehsud.

Khan, the Swat militant spokesman, claimed in his call that the weekend bombings in the valley were avenging the alleged killings of militants in army custody.

Residents reported finding 18 bodies -- most identified as Taliban -- in different areas of Swat on Saturday. Four more bodies were found Monday in fields near the valley's Barikot town, villagers said.

Lt. Col. Akhtar Abbas, an army commander in Swat, denied the army was killing militants in custody and speculated that the Taliban remnants were likely slaying wounded comrades rather than leave them behind to be captured and give up information to government forces.

Abbas said the homicide bombings were a sign of the Taliban's frustration -- not their strength.

"They are on the run. They are in hiding. God willing, we will wipe them out completely," he said.

No one claimed responsibility for Monday's bombing of a truck at a gas station in another area of the northwest.

Three children were among the seven people killed, and at least 15 were wounded, police said. Television footage showed bloodstained clothes and sandals scattered around the gas station in Charsada district, about 12 miles outside the main northwestern city of Peshawar.

Police officer Sifwat Ghayur said a timed explosive device had been loaded onto the truck in a package marked "medicine" without the driver's knowledge. The truck functioned as a taxi service between towns. Most of the dead were passengers.

Also Monday, gunmen assassinated the leader of the banned Sunni sectarian group Sipah-e-Sahaba, triggering rioting in the southern commercial capital of Karachi, police said.

Supporters of Sipah spiritual leader Ali Sher Haideri torched a bus and a gas station after he was gunned down in his car. The riots spread to two other cities.

Haideri's organization has been blamed for attacks against the country's minority Shiites, whom they regard as heretics. The U.S. State Department designated the group a terrorist organization in 2003.

Also Monday, India prime minister said there was "credible information" that terrorist groups based in Pakistan were planning new attacks in India.

After last year's attacks in Mumbai that killed 166 people, India put additional security measures in place but "continued vigilance" was needed, Manmohan Singh said at an internal security meeting in the Indian capital. He gave no further details.

Lashkar-e-Taiba, a Pakistan-based radical Islamist group, has been accused of masterminding the Mumbai attacks, waged by militants who traveled from Pakistan.