At least 30 soldiers have been killed and 18 others wounded in an explosion inside an army recruitment centre in northwest Pakistan.

"The bomb blast took place inside a military area, we have reports that several soldiers have been killed in the blast. There was an army parade at the time of the blast," Abdullah Khan, a senior police officer in Mardan, said on Thursday morning.

The army has carried out a series of offensives against the al Qaeda-linked Pakistani Taliban movement, which claimed responsibility for the attack. 

Al Jazeera's Kamal Hyder, reporting from Islamabad, said that the suicide bomber was dressed as a schoolboy.

"It is winter so most of the children are clad in heavy clothes, where he would have hid the bomb, and nobody would have suspected a boy dressed in school uniform to carry out the attack."

Our correspondent said that Mardan had seen a lot of trouble in the past.

"There was recently an assassination attempt on the deputy inspector general of police and also the Punjab regimental centre was attacked."

The boy apparently walked into the compound, officials said.

Military offensives

Pakistani Taliban fighters have managed to keep up pressure on the government with suicide bombings despite a series of military offensives against their strongholds.

Yusuf Raza Gilani, Pakistan's prime minister, condemned Thursday's attack at the Punjab Regiment Centre.

"Such cowardly attacks cannot affect the morale of the security agencies and the resolve of the nation to eradicate terrorism," he said in a statement.

Gilani's government faces pressure on several fronts. Public discontent is growing over official corruption, rampant poverty and power cuts.

Tensions between Islamabad and Washington are also running high over the case of Raymond Davis, who killed two Pakistanis in late January.

Davis, the US embassy in Islamabad says, is a diplomat who acted in self-defence when he shot two men in the middle of a busy Lahore street on January 27.

He thus enjoys diplomatic immunity and should be released according to international law and custom.

The Pakistanis say it is a matter for the courts to decide and and have moved to charge Davis with two counts of murder. Handing him over to the Americans would deepen anti-American sentiment in Pakistan.