The post was manned by members of the paramilitary Frontier Corps, Abbas said.
The attack comes after officials said on Tuesday that a US military strike in Mir Ali killed Abu Laith al-Libi, a senior al-Qaeda commander.
Separately on Friday two soldiers suffered minor injuries in a roadside bomb blast just outside Wana, the main town in the neighbouring tribal region of South Waziristan.
Pakistani troops are battling al-Qaeda and Taliban fighters in the tribal zone and in the northwest of the country.
Scores of fighters and government soldiers have been killed in the area in the past month.
A series of suicide bombings over the past 12 months has also killed at least 800 people.