THERE has been a lot of killing across Pakistan in the last few days.

Yesterday, in the restive Northwest Frontier Province (NWFP), men wearing army uniforms checked the identification cards of bus passengers before gunning down 22 of them after establishing they were Shia Muslims.

Just who carried out the attack near the town of Gilgit remains unclear, though Sunni militant groups inspired by al Qaeda often attack religious minorities such as Shi'ites in Pakistan.

That the incident barely made the main news bulletins was not just because such things have become a regular occurrence in the country but was also due to the audacious, headline-grabbing attack by armed militants who stormed a major Pakistani air force base near the capital Islamabad earlier in the day.

According to one Pakistan Air Force spokesman, the militants moved through a nearby village under cover of darkness before climbing a 9ft wall strung with barbed wire to break into the base.

Worryingly, some of the militants – like the gunmen in Gilgit – were wearing military uniforms.

"It's not the work of half-educated Taliban militants, but the handiwork of al Qaeda planners," insisted Mahmood Shah, a former brigadier general in the Pakistani army.

The speed with which Pakistan's Taliban movement, which has close links to al Qaeda, claimed responsibility for the attack was matched only by the denials from the Pakistani authorities to claims the Minhas base was home to part of Pakistan's nuclear arsenal.

Even if such denials prove accurate, that the militants were able to break into the base at all is remarkable. Some years ago, in the aftermath of the terrible 2005 South Asia earthquake that devastated parts of Pakistan and Kashmir, I was able to see for myself the extensive security measures taken to protect such installations.

It was from one such air base, Chaklala near Islamabad, a major helicopter relief effort was launched to fly supplies into the remote mountainous areas worst hit by the quake.

I well remember watching as US airmen pasted Stars and Stripes flags on to the sides of their Chinook helicopters, keen that the recipients of the aid knew exactly who was handling the delivery. Not that the thousands of families stuck high in the mountains, traumatised, cold and hungry, really cared who the providers were.

At face value there was nothing wrong with the US flag-waving. The Americans did themselves no end of political and PR good by getting in quick with a high-profile response. Among many Pakistanis, some even vehemently opposed to America's role in neighbouring Afghanistan, it wasn't uncommon on the streets of Islamabad to hear grateful remarks about the US effort.

"Someone has to save our unfortunate brothers and sisters," observed one shopkeeper I spoke to on Embassy Road in Islamabad one morning as the Chinooks thudded overhead en route to the quake's devastated epicentre. "Why not the Americans? This is not about war or politics."

Back then, of course, Washington and Islamabad were good pals, with the US military running many of its "war on terror" air operations in Afghanistan from the territory of their Pakistan ally.

Then along came that US Special Forces operation to kill Osama bin Laden, a military assault the Islamabad Govern-ment said was carried out on its sovereign soil without permission and which cast great suspicion over an allegedly duplicitous role played by Pakistan's own Inter Services Intelligence agency in harbouring the al Qaeda leader.

Since then, relations between the US and Pakistan have been chilled to say the least and, at worst, downright acrimonious.

Earlier this week, US Defence Secretary Leon Panetta further irritated Islamabad by highlighting the danger of terrorists gaining access to Pakistan's nuclear arsenal.

But behind such political scaremongering and hard talk the reality is somewhat different. Not only would such an apocalyptic nuclear scenario be highly unlikely, but there are now signs of a resurrected collaboration between the two nations over an imminent counter-terrorism operation across the Afghanistan-Pakistan border territories.

For weeks now the Pakistani press has been full of speculation over whether or not its army will launch a military offensive in the tribal province of North Waziristan which acts as a base for the most powerful Taliban-linked militant group, known as the Haqqani network.

In the last few days, Mr Panetta has pretty much confirmed such a push is about to commence, possibly as early as next month.

Pakistan, anxious not to rile its homegrown Islamic militants, has gone to some lengths to play down the US defence chief's remarks.

But others have said much the same thing, including Pakistan's own chief of staff, General Ashfaq Parvez Kayani, who used a meeting with John Allen, US commander of Nato forces in Afghanistan, last week to do just that.

Another senior Pakistani security official also urged US and Nato forces to seal the Afghan border from their side if Pakistan launched an operation against the militants. Taken together, such statements have been interpreted as indicating an offensive is now inevitable.

Doubters have a different take on how events might play out. Some security analysts remain unconvinced relations have really improved that much between Washington and Islamabad and that Pakistan is doing nothing more than running with the hare and hunting with the hounds by playing off both sides.

While the US would like Pakistan to target the Haqqani network, I suspect Pakistan will not primarily target that group.

Instead it will be the Pakistani Taliban that will be in Islamabad's sights. Not only will this enable Pakistan's security services to neuter the group's terrorist attacks on its soil but leave it the option of keeping its contacts within the Haqqani network intact in order to continue influencing events over the border in Afghanistan.

Whatever Islamabad's motives, we can expect an escalation of violence and a lot more killing in the months ahead.