Nine soldiers were killed and several others injured in the attack. The security forces launched a counter-attack and killed 10 militants, a security official said.
Eight more militants were injured in the clashes. The security forces launched a search operation in the region after repulsing the attack.
Security forces had cleared most of South Waziristan of Taliban militants during a major ground and air offensive in the 2009.
However, Taliban militants hiding in remote mountainous areas are still launching attacks on troops. Earlier yesterday, three soldiers and 11 militants were killed in clashes in the Batwar area of Bajaur tribal, security officials said.
The fighting occurred after the army launched an operation to push back Taliban militants who crossed over from Kunar province in Afghanistan on Friday and occupied Batwar village.
Officials told the media that several soldiers were missing and that troops had arrested eight militants. The fighting in Batwar area has so far claimed 50 lives, including 31 militants, three soldiers and two members of a pro-government tribal militia.
The reports could not be independently confirmed as journalists are barred from reporting from the tribal belt.