At least one policeman was killed and two were injured in a bomb attack in northwestern Pakistani town of Mingora on Thursday, media reported.
Two security guards were also injured in the remote controlled blast near a police checkpost and an Austrian-funded tourism centre, according to News Network International (NNI).
No group claimed responsibility for the blast yet.
The injured policemen, stated to be in critical condition, were taken to local hospital, the report said.
Attacks on security personnel have increased in northwest Pakistan since July when government forces stormed Islamabad-based hard-line Red Mosque and armed tribals in North Waziristan tribal region scrapped a peace deal with the authorities.
Mingora is an important town in mountainous Swat valley region that has seen several attacks against security personnel in recent weeks.