Twelve people died from their injuries Friday, the day after twin suicide bombings at Pakistan's largest arms and ammunition factory, hospital authorities said, as investigators interrogated at least a dozen suspects.

The latest casualties raised the death toll to 78 in the two synchronised attacks at the gates of the Pakistan Ordnance Factories (POF) in the garrison town of Wah Cantonment, 30 kilometres north-west of Islamabad.

"There are 103 injured now who are admitted at Pakistan Ordnance Factory hospital and various other hospitals in Rawalpindi," a senior police officer Rao Muhammad Iqbal told state-run newswire Associated Press of Pakistan.

Altogether 13 suspects, including three who were rounded up in the area shortly after the bombers blew themselves up among hundreds of POF workers as they left the sprawling complex on Thursday after a shift change, have been detained.

Initial reports said two bombers struck outside the factory but Rehman Malik, the security adviser to Prime Minister Yousaf Raza Gilani, said there had been three bombers.

"The fourth bomber was arrested before he could strike," he was quoted as saying by the English-language DawnNews television channel.

A security official, who spoke on condition of anonymity, said the suspected bomber was detained at a mosque close to the site of the carnage and a suicide vest and explosives were also seized.

"It is not clear so far whether he was waiting to strike his target or had changed his mind," he added.

Investigators said the attackers had layered ball bearings and nails onto the explosives to maximize the impact, adding that the explosives were of the same type as those used in last year's strikes on military targets in the nearby city of Rawalpindi, where Pakistan's army has its headquarters.

An air of gloom settled over the garrison town as a mass funeral was held Friday morning.

Hundreds of people gathered on the lawns of Wah's central mosque as coffins were lined up amid a somber atmosphere.

"It's incomprehensible as to how the militants can justify such gruesome acts," said Abdul Majeed, a middle-aged man who lost one of his relatives in the bombings.

Maulvi Omar, a spokesman for the Pakistani Taliban, claimed responsibility for the attacks on Thursday, saying these were carried out to avenge the ongoing military operation in Bajaur and Swat districts.

Omar warned the government that more attacks will be carried out in major cities if the military operations were not called off.

Pakistan Air Force units have been attacking militants in Bajaur tribal district bordering Afghanistan since the beginning of August.

Hundreds of militants have been killed in the fighting, while around 250,000 people fled from the conflict zone after the authorities gave calls for evacuation to avoid collateral damage.

But the operation came only after the new civilian government's imitative to offer peace talks with the militants after it took over in March failed.

"These elements cannot see democracy to flourish and the country to become prosperous. Is it just to kill unarmed innocent women children and the lone bread-winners of their families," Prime Minister Gilani told reporters in Islamabad on Friday.

We do not want to give the impression that these people are succeeding and the democratic forces are failing in Pakistan, he added.

Gilani vowed to mobilize the public against terrorism and start a debate in the parliament on how to tackle the issue of militancy.