Officials had earlier said that one soldier was killed when fighters fired rockets on the FC convoy.
But Mehsud said latest information revealed that it was a suicide attack and two soldiers were killed.
The attacks came hours after police killed four Taliban loyalists in a gunfight in the town of Bannu, 80km northeast of Tank.
Both Tank and Bannu lie in North West Frontier Province [NWFP], a gateway to the volatile Waziristan tribal region on the Afghan border.
Violence has been increasing in parts of NWFP over the past year or so, evidence, some analysts say, of "Talibanisation", or the spread of militant influence from remote tribal regions on the Afghan border to more developed, populous areas.
Two soldiers were killed in a roadside bomb explosion in Tank on Saturday.
Pakistan's tribal belt along the Afghan border is a hotbed of support for al-Qaeda and the Taliban, many of whom took refuge in the lawless area after US-led forces routed the Taliban government in Afghanistan in 2001.