Pakistan suffered its fourth big militant attack in eight days yesterday when a suspected suicide bomber struck a military convoy, killing 41 people near the northwestern region of Swat.

The bomber, said to be aged about 13, flung himself at one of three military vehicles passing through a busy market in the district of Shangla, near Swat, which the Pakistani Army claimed to have cleared of militants in an offensive this year.

There was no immediate claim of responsibility for the attack, which killed six soldiers and thirty-five civilians, and followed two other suicide bombings last week and a commando-style raid on the army’s headquarters at the weekend.

It bore all the hallmarks of the Pakistani Taleban, which claimed responsibility yesterday for attacking the army headquarters in Rawalpindi on Saturday and taking 42 people hostage inside for 22 hours. Twenty-three people were killed in that attack, including nine militants, three hostages and eleven soldiers.

The army said that the Taleban appeared to be trying to intimidate it into calling off an imminent attack on the tribal region of South Waziristan, considered the main militant stronghold in Pakistan.

“It is now a matter of military judgment what is the appropriate timing in the best national interests,” Major-General Athar Abbas, the army spokesman, told reporters about the timing of that assault. “These are the signs of desperation of an organisation that is staring defeat in the face.”

He said that the attack on the army headquarters had been planned from South Waziristan and directed by a Pakistani Taleban commander called Wali ur-Rahman, whose phone calls to the attackers had been intercepted.

The ten attackers had planned to take senior military officers hostage to demand the release of 100 captured militants, General Abbas said. Five of the attackers were ethnic Pashtuns while the other five were from Punjab province, including their leader, Mohammed Aqeel, who was wounded and captured.

He said that the Punjabis were from splinter groups of banned Punjab-based militant outfits such as Jaish-e-Mohammed and Lashkar-e-Janghvi, but he denied that there were militant “safe havens” in Punjab, Pakistan’s biggest and economically most important province.

The military has responded over the past two days by resuming airstrikes on Taleban bases in South Waziristan and Bajaur, another tribal region, killing an estimated 31 militants.

The army has been preparing for the assault on South Waziristan since June, moving about 28,000 troops into the area in the hope of repeating the success of a campaign in April to drive the Taleban out of Swat.

Analysts say that the South Waziristan operation will be far tougher because the Taleban have about 10,000 men entrenched in hostile terrain and able to slip easily across the Afghan frontier. Some also fear that the timing and scale of the operation could be affected by a dispute between the army, the Government and the United States over the $7.5billion (£4.7billion) American aid package.

The Bill, which triples civilian aid to Pakistan, was approved by Congress ten days ago and is supposed to be signed into law by President Obama today. It will become law automatically if he does not sign it. It has provoked widespread anger in Pakistan, where the army and many politicians say that conditions attached to it amount to a humiliating violation of sovereignty. Shah Mehmood Qureshi, the Foreign Minister, has flown to the US to try to salvage the package.

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