ISLAMABAD — Taliban fighters armed with rifles and rocket launchers killed at least eight Pakistani soldiers during an ambush early Wednesday in South Waziristan, near the Afghan border, military officials and Taliban commanders said.

Large-scale Taliban assaults against the Pakistani Army are relatively rare in South Waziristan, where the army conducted a major operation in 2009.

But tensions have risen in recent weeks amid a flurry of drone strikes by the CIA and speculation that the army is planning a drive into neighboring North Waziristan.

Exact details of what happened during Wednesday’s attack were unclear.

A spokesman for Tehrik-e-Taliban Pakistan, commonly known as the Pakistani Taliban, said the group’s fighters killed 20 soldiers during an assault on a post in the Serwakai district.

The spokesman, Ehsanullah Ehsan, said seven additional soldiers had been kidnapped and were later beheaded.

A senior military official, speaking on condition of anonymity, said eight soldiers were killed and six wounded during a broader ‘‘search and clearance’’ operation that targeted Taliban hide-outs and uncovered a major weapons cache. At least 18 militants were killed in the fighting, he said.

The conflicting accounts were typical of the region, where few reporters can safely operate and both sides in the conflict manipulate the flow of information.

Since its 2009 offensive in South Waziristan, the army has controlled the main roads and villages in the mountainous ethnic Mehsud areas that once formed the Pakistani Taliban’s main stronghold.

Many fighters fled into North Waziristan during the operation, but they have crept back in recent years.