Pakistani troops training
© Anjum Naveed/APPakistani troops training in the tribal region along the Afghan border. The army said it has launched a 'comprehensive operation' against foreign and local militants in North Waziristan.
Up to 30,000 troops thought to be involved in operation to destroy bases of terrorist groups operating from North Waziristan

A long-awaited military campaign to destroy militant safe havens in a Taliban-dominated part of Pakistan's borderlands began , years after the US first demanded action.

The army said it had launched a "comprehensive operation against foreign and local terrorists who are hiding in sanctuaries in North Waziristan", the troubled tribal region that has served as a staging area for attacks across Pakistan and Afghanistan.

Military sources said as many as 30,000 troops could be involved in the operation to secure the border region, which the army believes must be completed before the end of Nato combat operations this year in Afghanistan.

An official statement said "Operation Zarb-e-Azb" had been launched "on the directions of the government", but the decision follows months of public controversy over the issue, with leading politicians arguing any attempt to seize control of the area would provoke a violent backlash by the Pakistani Taliban in the country's cities.

Pakistan's prime minister, Nawaz Sharif, had instead tried to negotiate a peace deal with militants, something most experts said had no chance of success given the record of militants breaking ceasefires.

Sharif's obstinacy in the face of army demands for North Waziristan to be dealt with before summer has exacerbated tensions between Pakistan's civilian and military leaderships, who have clashed over the treason trial of former military ruler Pervez Musharraf.

The military statement said the country could not afford to wait any longer. "Using North Waziristan as a base, these terrorists had waged a war against the state of Pakistan and had been disrupting our national life in all its dimensions, stunting our economic growth and causing enormous loss of life and property," it said.

Pakistan's military had already ramped up pressure on militant groups in North Waziristan in recent weeks, launching air strikes and limited ground operations which it described as limited acts of retaliation against Taliban attacks.

The latest came early on Sunday when the army claimed fighter jets killed 80 terrorists, most of whom it said were Uzbeks involved in last week's lethal attack on Karachi's airport. Military sources said Abdul Rehman, a senior commander from the Islamic Movement of Uzbekistan who is said to have masterminded the airport attack, was among the dead.

North Waziristan is part of a swath of forbidding, mountainous border territory that fell under Taliban control after militants fled there from Afghanistan following the US-led invasion of 2001.

It soon became a global hub for a plethora of terrorist groups, including al-Qaida and the Pakistani Taliban.

The presence of a large safe haven next to Afghanistan enraged bWashington and Kabul who complained the region was being used to hatch plots, train fighters and prepare suicide bombers who could cross the border to kill Afghan and Nato troops.

But Pakistan refused to act, even after the attempt by a Pakistani American terrorist to bomb New York's Times Square was traced back to the Pakistani Taliban in North Waziristan.

In 2011 the North Waziristan-based Haqqani Network, an Afghan militant group, launched a rocket attack on the US embassy in Kabul.

In response the White House expanded the use of missile strikes by unmanned drones to kill suspected militants, although the increase in strikes caused outrage in Pakistan.

Pakistan's refusal to act in North Waziristan reinforced suspicions that it continues to support and protect some militant groups, including the Afghan Taliban, in order to gain influence in Afghanistan, a country historically feared by Islamabad because of its refusal to drop claims to Pakistani territory and long-standing ties with arch enemy India.

The army argued it was taking action, methodically clawing back control of parts of the tribal north-west that had slipped into militant hands by launching major operations in the Swat Valley and South Waziristan.

Some observers remain sceptical despite Sunday's announcement. They argue the Haqqani Network and other militant groups regarded as useful allies are likely to be left untouched by the operation or will simply move into unsecured parts of western Afghanistan.

On Sunday the army insisted it would "eliminate these terrorists regardless of hue and colour".

Despite the dangers posed by North Waziristan, many analysts, including one senior western security official in Islamabad, warn an operation may only succeed in forcing dangerous militants into other parts of the country, including the already turbulent city of Karachi where the Pakistani Taliban has made dramatic inroads in recent years.

They say the police are simply not prepared to fight an urban insurgency.

Speaking on local television defence minister Khawaja Asif said "terrorists may carry out attacks, we have to be watchful". But he vowed that the operation would be carried through "to its logical conclusion".

"Any group that uses Pakistan's soil for terrorism will be eliminated, the operation will continue till the complete destruction of terrorism," he said.