DERA ISMAIL KHAN: Taliban ambushes and bombings killed at least seven Pakistani soldiers in the northwest as the military made a new push into the militants' last major stronghold near the border with Afghanistan, intelligence officers said Sunday.

Pakistan began a major offensive in North Waziristan last summer to drive out Pakistani Taliban and other extremist Islamist militants who launch attacks on government and civilian targets.

The army is meeting fierce resistance as it moves further into the lower-lying areas of the Shawal Valley, the Taliban's last stronghold, military officials said.

Pakistan's army chief, Gen. Raheel Sharif, visited troops on Friday and said the initial phase around the surrounding peaks of the Shawal Valley was successful and it was now time to begin a final push into the lower areas.

"We will not stop unless we achieve our end objective of a terror-free Pakistan," he said.

Militants ambushed a military convoy on Saturday in the valley's Pir Ghr area, killing two soldiers and wounding three others, intelligence officials said on condition of anonymity because they were not authorised to speak to the media.

The Pakistani Taliban claimed responsibility for the attack, with spokesman Azam Tariq saying five soldiers were killed.

The intelligence officials added that troops moving from both the North and South Waziristan sides into the Shawal Valley were encountering tough resistance from militants.

The heavily forested ravines in the area are dotted with Taliban hideouts and the area is a key smuggling route into neighbouring Afghanistan.

Two other attacks in the northwest killed five more soldiers outside the Shawal Valley.

The first, a remote-controlled bomb attack on army vehicles in North Waziristan, killed three and injured six.

A second bomb attack on a military vehicle in South Waziristan killed two others, the military officials said.

The Pakistani Taliban had controlled almost all of the northwestern region of North Waziristan before troops launched their offensive last year.

Many militants have fled to other parts of Pakistan, and some into Afghanistan, complicating the US-backed Kabul government's fight against its own Taliban insurgency.