Pakistani troops have killed a number of militants in the restive tribal region bordering Afghanistan.

Pakistani army spokesman (Major General Waheed Arshad) Saturday said militants have have suffered heavy casualties near the town of Ladha in the South Waziristan tribal area. He said he did not have official figures.

The casualties occurred during two days of fighting that began on Wednesday, as Pakistani forces targeted top al-Qaida and Taliban leaders in the region.

On Friday, the U.S. Chairman of the Joint Chiefs of Staff Admiral Michael Mullen expressed concern about the presence of al-Qaida safe havens in Pakistan, saying the militants are launching attacks in neighboring Afghanistan - but, also - inside Pakistan.

Admiral Mullen said the U.S. is mindful that Pakistan is a sovereign nation and that it is up to Pakistani President Pervez Musharraf and his military advisors to confront the problem directly.

President Musharraf has warned the U.S. against any unilateral move into Pakistan's tribal region to hunt down al-Qaida or Taliban militants. He told a Singapore newspaper ("The Straits Times" on Friday) that such move would be considered a breach of sovereignty.