Islamabad, Pakistan (CNN) -- At least 12 people were killed when a teenage suicide attacker blew himself up Saturday at a security checkpoint in northwest Pakistan, officials said.
Twenty more were injured in the blast, most of them civilians, said Muhammad Iqbal Khattak, a local official.
The attack took place in Khar, the main town in Bajaur, one of seven districts in Pakistan's tribal region. It occurred on a road leading to a nearby military base, Khattak said.
Two of the fatalities were security personnel, according to an official who asked not to be identified because he is not authorized to speak to the media.
The official said panicked security personnel fired shots in the air after the blast.
A local government official and an intelligence official said the attack targeted a location in the village of Muhammaed Khel in the Datta Khel region of North Waziristan, one of seven districts in Pakistan's tribal region.
The two officials asked not to be named because they are not authorized to speak to the media. The strike comes on the heels of an escalation of drone attacks in North Waziristan targeting al Qaeda and Taliban compounds.
U.S. officials normally do not comment on suspected drone strikes, which have caused tension between Pakistan and the United States in the past. The United States is the only country operating in the region known to have the ability to launch missiles from drones, which are controlled remotely.
Journalist Nazar Ul-Islam contributed to this report.