By Jon Boone in Islamabad and Jason Burke in New Delhi/ The Guardian –

A drone strike earlier this week killed al-Qaida‘s second in command, Abu Yahya al-Libi, US officials have claimed, hours after Pakistan officially reprimanded a top US diplomat, declaring such attacks to be against international law and in violation of its sovereignty.

Abu Yahya al-Libi has had a bounty on his head from the US government for years. Photograph: Ho/AFP/Getty Images

Libi “was among al-Qaida’s most experienced and versatile leaders”, a US official said, according to Reuters. It was also being claimed on Tuesday night that a Pakistani Taliban leader, confirmed Libi’s death, saying it was a “big loss”

But earlier Richard Hoagland, the US chargé d’affaires in Islamabad, was called into the foreign ministry on Tuesday after a recent increase in missile attacks by remotely controlled aircraft. He was told “drone strikes represented a clear red-line for Pakistan,” a government statement said. The diplomatic step comes with Islamabad looking ever more isolated in the region as the US seeks to reduce its dependence on Pakistan.

The timing of Pakistan’s stand has highlighted the immense stresses the drone campaign is putting on efforts by Washington and Islamabad to patch up their deeply distrustful relationship.

Earlier Pakistani officials had claimed that Libi, a high-profile al-Qaida terrorist who once escaped from a top security US military prison, may have been killed by a drone strike on Monday on Hasokhel, a village in North Waziristan, where Taliban and al-Qaida militancy thrives. The attack was reported to have claimed up to 18 lives.

Libi enjoyed legendary status within the movement and second only in authority to al-Qaida leader Ayman al-Zawahiri. If, as the US claims, the strike was successful, it again underlines the importance the Obama administration placed on drones in its fight against terrorists.

Al-Qaida can often wait weeks or even months to admit the deaths of its senior commanders.

Syed Amid, a tribal elder from the area, said he was not aware whether Libi was killed, but said that up to 18 militants had been killed and that “some foreigners were among the dead”, including Arabs.

But a Pakistani intelligence official said he believed Libi was in the house that was targeted by missiles and that one of his vehicles was also destroyed.

Although drone strikes are extremely unpopular within Pakistan some people living in the semi-autonomous tribal areas where the strikes are concentrated say they support them.

Nazim Dawar, a social worker from the town of Mir Ali, said there are never any popular demonstrations in his area against drones.”It is only the people in the cities like Islamabad, Karachi and Peshawar that agitate against them,” he said.

“Yes, some ordinary people do get killed, but it is mostly the Taliban who get killed in these attacks.”

But Mohammad Iqbal, a labourer from North Waziristan, said the strikes were “pulling apart the social and economic fabric” of the tribal areas.

“About half the people have had to move to other areas to escape the drones,” he said. “Anyone who stays lives in terror they will be killed.”

For Pakistan, the attacks have to stop. As the country’s foreign ministry pointed out to Hoagland, the country’s parliament had “emphatically stated [drone strikes] were unacceptable”.

“He was informed that the drone strikes were unlawful, against international law and a violation of Pakistan’s sovereignty,” a government statement said.

Earlier this year Pakistan’s parliament unanimously decided on a set of demands the government should make of the US. They included an end to drone attacks, higher tariffs for Nato supply trucks crossing Pakistani territory and a public apology for a disastrous incident in November when US troops killed 24 Pakistani soldiers.

The accident prompted Pakistan to close its borders to trucks carrying vital military supplies to US and Nato forces in Afghanistan. The closure has still not been overturned, despite several false hopes.

US diplomats are adamant there will be no ending of the drone campaign. The best Pakistan can hope for, they say, is some sharing of intelligence and inclusion in target selection.

And they are furious with Pakistan’s behaviour, not least during the recent Nato conference in Chicago where it had been hoped Pakistan would announce it would restart cooperation on supply lines and counter terrorism.

Drone strikes, which had been in abeyance, restarted with a vengeance after the failure of the Chicago summit, with three attacks in three days starting on Saturday, that have been reported to have killed up to 29 people.

Many in Pakistan’s security establishment believed the US-led war in Afghanistan would grind to a halt without the vital supply lines from the port of Karachi and then overland to Kabul and Kandahar.

But that has not come to pass, with the US and its allies instead switching to the far longer and more costly route through Russia and Central Asia into northern Afghanistan.

On Monday Nato announced that the former Soviet republics had agreed that in addition to bringing vital supplies into Afghanistan, the alliance would be permitted to move a decade’s worth of equipment out through their territory as well.

It had been thought Pakistan’s cooperation would be vital for the safe withdrawal of Nato kit.

The Pakistani reprimand came as the US defence secretary, Leon Panetta, was in Delhi to encourage India – Pakistan’s arch enemy – to become more militarily involved in Afghanistan, including doing more to train Afghan soldiers.

For decades Pakistan’s entire foreign policy has been geared to reducing Indian influence in Afghanistan out of fear it would face a two flank struggle if ever got into another military confrontation with a traditional rival it has already fought three wars against.

“Before the US saw Pakistan as the best partner to stabilise Afghanistan and India was being told by the US ‘don’t do too much’ [in Afghanistan], don’t upset the Pakistanis’. Now that has changed,” said Dr C Raja Mohan, at Delhi’s Observer Research Foundation. The local Times of India newspaper reported on Tuesday that India is now close to signing huge deals for artillery and helicopter gunships worth more than $2bn from the US.