ISLAMABAD An Islamist group that claimed responsibility for bombing the Marriott Hotel in Islamabad had not previously been heard of, but Pakistani intelligence eavesdroppers heard al Qaeda operatives celebrating the attack.
The suicide truck bomb that killed at least 53 people and gutted the hotel on Saturday has raised fresh fears about worsening security in nuclear-armed Pakistan, a key U.S. ally.
A group calling itself Fedayeen Islam (Partisans of Islam) claimed responsibility in a call to an Islamabad-based correspondent for al Arabiya, an Arab news channel.
"It's either new or it might be a distraction," said a senior intelligence officer. "What we do know is that there was a lot of celebration among the lower ranks of al Qaeda."
Three members of a Pakistani Islamist group known for al Qaeda ties were caught in Gujranwala, a city in central Punjab province, as a result of electronic surveillance hours after the Marriott blast, according to another intelligence officer.
Arabiya reported that the group that claimed responsibility issued several demands, including that Pakistan ends cooperation with the United States.
Many Pakistanis already say that the alliance with the United States incites Islamist militant violence and Pakistan should not be fighting "America's war".
On Tuesday, the military said troops backed by artillery and helicopter gunships killed 50 militants in Darra Adam Kheil, a tribal region close to the northwestern city of Peshawar. Ten more militants were killed in Swat, a northwestern valley.
Five people were killed and several wounded when a protest by thousands of people against worsening security in Swat turned violent. Demonstrators set fire to three banks and security forces fired to disperse the crowd, police and witnesses said.
The army has also launched a major offensive in the Bajaur region on the Afghan border, and said hundreds of militants have been killed there since late August.
Despite this, the United States has shown impatience and wants more done. Missile attacks by pilotless drone aircraft against militants on the Pakistani side of the border have multiplied.
Pakistan warned its ally to desist after the United States launched a commando raid that killed 20 people, including women and children, in a border village on Sept. 3, the first operation by U.S. ground troops on Pakistani territory.
Pakistani troops have opened fire twice since to force U.S. helicopters to turn back to Afghan airspace.
The latest incident was on Sunday, according to a security official, although there has been no official confirmation.
President Asif Ali Zardari is due to hold talks with U.S. President George W. Bush in New York on Tuesday.
In an interview in the United States aired on Pakistani television, Zardari said cross-border actions on Pakistani territory complicated the situation.
"Give us the intelligence and we'll do the job," he said.
"It's better done by our forces than yours because if you do incursions, the constituency which I'm trying to appease, they'll take it as a foreign war," he told his American interviewer.
Former Prime Minister Nawaz Sharif said this week the government should reject U.S. pressure, halt offensives and negotiate peace.
Some analysts saw the Marriott attack helping to convince people that it was Pakistan's war, not just America's.
The United States is Pakistan's biggest aid donor and its support will be crucial if Pakistan is to avoid bankruptcy.
Moody's Investor Service downgraded the outlook on Pakistani debt to negative on Tuesday.
The rupee has lost 21.2 percent against the dollar this year and is trading around all-time lows. The main stock index has lost about 35 percent this year and had been propped up by a floor since last month.
Compounding a sense of crisis, gunmen kidnapped Afghanistan's top diplomat to Pakistan, Abdul Khaliq Farahi, after killing his driver in an ambush on Monday in Peshawar.
Afghan Defense Minister Abdul Rahim Wardak said on Monday Pakistan and Afghanistan were discussing a joint force to combat militants on both sides of their border. A Pakistani military spokesman said he was not aware of any such proposal.
(Additional reporting by Augustine Anthony and Kamran Haider)