Islamabad  - Pakistani forces have swiftly overrun most Taliban redoubts in their South Waziristan offensive but the gains might not ensure eradication of terror networks in the region.

Under what they term a "strategic retreat," the Taliban have fled towns and villages to save their men and ammunition and continue to fight from remote valleys and neighbouring tribal districts.

More than 30,000 ground troops moved last month into the heartland of Tehrik-e-Taliban Pakistan (TTP) - an umbrella organization of more than a dozen militant groups blamed for a series of suicide attacks across Pakistan since 2007.

Tough resistance was expected from up to 10,000 well-trained guerrilla fighters from the mainly ethnic Pashtun Mehsud tribe and a few hundred from al-Qaeda linked groups.

To the surprise of many, however, the operation has been relatively easy so far, with the troops, recording only 46 fatalities. Military officials say an announcement of final victory might come in next few weeks.

Fighting small rearguard actions, the Taliban deserted their bunkers and posts in the major towns, leaving space for the troops to occupy.

An intelligence official overseeing the spying operations in the district said many groups of Taliban were spotted moving to Shawal, a remote and inaccessible area near the Afghan border.

Dense forests and ravines make the Shwal valley in North Waziristan a perfect terrain for a lethal guerrilla war.

"Our troops will not enter the area, at least for now. It's a very difficult area," said the official, who spoke on condition of anonymity.

Other fighters slipped away into at least four other tribal districts - Orakzai, Mohmand, Bajaur and Kurram - where the TTP controls large swaths of territory.

"The militants started to shift their kin and cattle, and ammunition to other tribal districts after the government announced an operation in South Waziristan in May," said the intelligence official.

The former commander of Pakistan's elite commando force, Javed Hussain, said the force involved in the offensive is too small to block the secondary routes and traditional smuggling channels used by the Taliban to flee.

The troops have so far focused on securing the main town along the three main roads and the bases lost to the Taliban in previous encounters during their three-pronged operation, Hussain said.

The Pakistani government said forcing the militants to flee has been a success, pointing out the rebels have lost dozens of training facilities, including one to groom suicide bombers.

But intensified suicide bombings and raids on civilian and sensitive military installations across the country in recent weeks tell a different story.

It appears the Taliban's ability to hit at will has not been minimized - more than 300 people killed in such attacks in October bear testimony to this.

Azam Tariq, a Taliban spokesman, vowed to orchestrate a "long guerrilla war" by early next year, after an end to the snowfall that blocks the important passes, making the movement across the mountainous district of around 6,620 square kilometres very difficult.

Analysts warn the Taliban strategy could have "dangerous consequences" for the Pakistani forces, who claim to have killed around 500 fighters so far.

"The Taliban might regroup and return to South Waziristan with more force and make the troops continually bleed with deadly ambushes, raids and roadside bombings," said military-officer-turned analyst Zahid Ahmad Bangash.

"The government needs to widen the war and chase the fleeing Taliban wherever they go, otherwise the entire objective of the operation would be lost," added Bangash.

For Pakistan a larger military campaign would mean moving out some of the thousands of soldiers struggling to maintain the control they regained from Taliban in north-western Swat region after intense fighting in the first half of this year.

Even if Pakistan stretches its available strategic resources to the maximum, a larger offensive in the tribal region could still be a complicated affair.

Chasing Taliban into North Waziristan would be considered violation of a two-year-old peace deal the government renewed in September to keep the militant commander Hafiz Gul Bahadur neutral in the assault against the TTP.

His enraged followers could join their Taliban colleagues in South Waziristan, making the war bloodier than it has been till now, analysts said.

"Things are really complicated and that's why the Pakistani forces are taking on the Taliban cautiously, gradually and piece by piece," said Mehmood Shah, a former security chief in the tribal region.

"Clearing up the mess we created over the years by nurturing the Taliban in our tribal region will take some time. We need to show patience," Shah noted. (dpa)