Double suicide attack kills 45

The scene of a bomb attack

About ten of those killed were soldiers, local police chief Parvaiz Rathore said.

It was the fourth major attack in the country this week, indicating that Islamist militants are stepping up their violence after a period of relative calm.

Hours later, another explosion shook Lahore, but there were no reports of serious injuries. Police said it apparently resulted from loose explosives – not a packed bomb – left beside a house.

The two suicide bombers, who were on foot, struck RA Bazaar, a residential and commercial neighbourhood where several security agencies have bases. Security forces swarmed the area as thick, black smoke rose into the sky and bystanders rushed the injured into ambulances.

Video shot with a mobile phone just after the first explosion showed a large burst of orange flame suddenly erupting in the street, according to GEO TV, which aired a short clip of the footage taken by Tabraiz Bukhari, who could be heard shouting: "Oh my God! Oh my God! Who are these beasts? Oh my God!"

Witness Afzal Awan said some of the wounded were missing limbs and lying in pools of blood after the explosions. He added: "I saw smoke rising everywhere. A lot of people were crying."

No group immediately claimed responsibility, but suspicion quickly fell on al-Qaeda and the Pakistani Taleban.

The militants are believed to have been behind scores of attacks in Pakistan over the past several years, including a series of strikes that began last October and went on for about three months, killing some 600 people in apparent retaliation for an army offensive along the Afghan border.

In more recent months, the attacks have been smaller, fewer and confined to remote regions near Afghanistan.

But on Monday, a suicide car bomber struck at a building in Lahore where police interrogated high-value suspects – including militants – killing at least 13 people and wounding dozens. The Pakistani Taleban claimed responsibility.

Also this week, suspected militants attacked the offices of World Vision, a United States-based Christian aid group, in the northwest district of Mansehra, killing six Pakistani employees, while a bombing at a small, makeshift cinema in the north-west city of Peshawar killed four people.

Rana Sanaullah Khan, the law minister for Punjab state, where Lahore is located, said the fresh attacks were a "sign of desperation" by the militants. "We broke their networks. That's why they have not been able to strike for a considerable time," he said.

However, the attacks show the loose network of insurgents angry with Islamabad over its alliance with the US retain the ability to strike throughout Pakistan, despite pressure from army offensives and American missile strikes.

The violence also comes amid signs of a Pakistani crackdown on the Afghan Taleban and al-Qaeda operatives using its soil. Among the militants known to have been arrested is the Afghan Taleban's No 2 commander, Mullah Abdul Ghani Baradar.

The Pakistani Taleban, meanwhile, are believed to have lost their top commander, Hakimullah Mehsud, in a US missile strike in January. The group has denied Mehsud is dead but has failed to prove he's still alive.

Militant attacks in Pakistan frequently target security forces, though civilian targets have not escaped.

In the bloody wave of attacks that started last October – coinciding with the army's ground offensive against the Pakistani Taleban in the South Waziristan tribal area – Lahore was hit several times.

In mid-October, three groups of gunmen attacked three security facilities there, a rampage that left 28 dead. Then twin suicide bombings at a Lahore market in December killed about 50 people.