Suicide bombers in Charsadda have targeted new military recruits in what the Taliban called 'the first of many' reprisals for the killing of Osama bin Laden Reuters

A double bomb attack on a military training centre in north-west Pakistan has killed at least 80 people in the first militant riposte since US troops killed Osama bin Laden on 2 May.

The Pakistan Taliban claimed responsibility for the bombing, which ripped through a crowd of recruits at the gates of a Frontier Corps base in Shabqadar, Charsadda district, 22 miles (35km) north of Peshawar.

"This is the retaliation for the killing of Osama bin Laden. Pakistani and US forces should be ready for more attacks," a Taliban spokesman told CNN.

Young recruits were boarding buses at the gates of the military academy at 6am on Friday, preparing to return home after a nine-month training course, when two suspected suicide bombers struck.

"It was a suicide bombing," Nisar Sarwat, the police chief of Charsadda, told Reuters, saying one of the bombers was on a motorcycle and police were investigating reports the other attacker was too. The two giant explosions shredded the recruits' white minivans, killing their occupants and scattering luggage across the market.

"There was a big blast," a fruit seller told the Associated Press. "I saw smoke, blood and body pieces all around."

"The first blast occurred in the middle of the road, and after that there was a huge blast that was more powerful than the first," said Abdul Wahid, a 25-year-old recruit hurt in the explosions.

At least 80 people – 66 of them military recruits – were killed and more than 100 injured. The death toll is expected to rise.

The British foreign secretary, William Hague, condemned the attack as "cowardly and indiscriminate, killing many innocent bystanders and targeting those who serve to protect Pakistan". The US embassy in Islamabad issued a statement saying it "respected the nation's sacrifices" and would stand with Pakistan in the struggle to "disrupt, dismantle, and defeat al-Qaida and allied terrorist organisations".

It was the largest attack since a team of US navy Seals stormed a suburban house in Abbottabad on 2 May, killing Bin Laden and four other people in a dramatic raid that has triggered political turmoil inside Pakistan and a flurry of uncomfortable questions from outside the country.

Pakistan's army is facing unprecedented criticism while politicians in Washington, including President Barack Obama, say they want to know how the al-Qaida leader stayed on the run in Pakistan for at least six years.

The army chief, General Ashfaq Kayani, is due to address a closed session of parliament to explain the circumstances around the controversial US raid.

On Thursday, the prime minister, Yousaf Raza Gilani, warned of a "trust deficit" between the US and Pakistan and said that co-operation between the CIA and Pakistan's ISI had broken down. "Traditionally the ISI worked with the CIA," he told Time magazine, but "what we're seeing is that there's no level of trust."

However, the uneasy relationship has shown some signs of resuscitation, with reports that US officials were allowed access to Bin Laden's three widows in Pakistani custody. The women were not co-operative.

Charsadda district is close to the Mohmand tribal agency, where the army recently launched a major offensive against the Taliban, the latest of a two-year battle to flush militants from the Afghanistan border area.

The Frontier Corps, a paramilitary force drawn mostly from the Pashtun tribes, is not fighting in Mohmand, but has been targeted in Taliban attacks across the north-west in recent years.