Pakistani officials say at least 30 people have been killed and more than 100 others wounded in sectarian clashes between Sunni and Shi'ite Muslims in northwestern Pakistan.

Officials Saturday say the clashes began Friday when unidentified gunmen opened fire in Parachinar, the main town in the Kurram tribal region near the Afghan border.  The officials say armed men have been attacking each other since, with assault rifles and other weapons.

Authorities have imposed an indefinite curfew in parts of the town.

In a separate development, the Pakistani army says it is preparing to soon launch a major operation in the northwestern Swat Valley to clear out militants who have infiltrated from areas along the Afghan border.

The chief of the military operation told reporters at army headquarters in Rawalpindi today that hundreds of well-armed militants have moved into the area from the neighboring Waziristan tribal region. 

The military officer said the fighters have also come from Afghanistan in support of radical cleric Maulana Fazlulla.

He said police operations had failed to stop the militant build-up in the region, but that he hoped to open the tourist resort to the public by the end of next month.

Unrest in the Swat Valley erupted last month when the pro-Taliban cleric declared holy war against the government, spreading his message through a pirate FM radio station.  Over the past two weeks, militant fighters seized control of several towns and police stations without much resistance from the army.

Pakistani President Pervez Musharraf has used the militant actions to justify imposing emergency rule.

Some information for this report was provided by AFP, AP and Reuters.