Pakistan troops prepare to leave to patrol around Bannu, a town on the edge of Pakistan's lawless tribal belt Waziristan, on Saturday. (Ijaz Muhammad/Associated Press)

Fierce fighting between military forces and the Taliban is underway in Pakistan's South Waziristan region, officials said Saturday.

The army said it has moved about 30,000 troops into the area, which is the heart of Taliban activity.

Pakistani army spokesman Maj. Gen. Athar Abbas said it was too early to discuss what sort of resistance the army was meeting.

Journalists near South Waziristan said troops are moving into the mountainous region from three directions.

The offensive comes after a wave of deadly Taliban attacks. More than 170 people have been killed in several co-ordinated strikes against targets in Pakistan cities in the last two weeks

This latest ground operation follows weeks of air and artillery strikes against militant targets in the region, which lies close to the Afghan border. The army has been surrounding the area for the last three months and cutting off key supply routes used by militants.

Thousands of civilians have fled the area in anticipation of the offensive.

Up to 150,000 civilians left in recent months after the army made clear it was planning an assault, but as many as 350,000 remain.

With files from The Associated Press