Local officials in northwest Pakistan say a suicide bomb attack on a tribal police patrol has killed at least 18 people, including 11 officers.
Officials say the bomber detonated his explosives near a police vehicle on the main highway in the Khyber tribal agency. At least 15 people were wounded.
No group has claimed responsibility for the bombing.
The highway in Khyber agency is one of the busiest transportation routes into Afghanistan. Taliban militants frequently stage attacks on local Pakistani security forces, as well as on NATO trucks carrying supplies for troops in Afghanistan.
Since last year, Pakistani troops have targeted militant hideouts in several parts of the tribal region, including Khyber.
Pakistan's military on Wednesday said one of its attack helicopters crashed in a remote area of Khyber, following a battle with militants. The fate of the helicopter's crew is not yet clear.
Meanwhile, there are still conflicting reports about whether Pakistani Taliban leader Hakimullah Mehsud was killed by a recent U.S. drone strike.
Pakistan's interior minister said Wednesday there is "credible information" that Mehsud is dead, but he could not confirm it. Rehman Malik did not describe what information led him to that conclusion.
After a mid-January missile strike on a compound in South Waziristan, intelligence officials said they believed Mehsud was seriously wounded and later died. Similar reports of his death followed other missile strikes in the tribal region.
Taliban spokesmen denied the reports and after the initial strike, released an audio recording that they said proved Mehsud is alive. But media reports have continued to quote anonymous Pakistani and U.S. intelligence officials who say they believe he has died.
Hakimullah Mehsud's predecessor, Baitullah Mehsud, was killed in a U.S. missile strike in South Waziristan last August.