At least three people have been killed and seven injured in a suicide bombing in north-west Pakistan, police say.
Security forces are on alert across Pakistan
Police say the bomber killed himself, a policeman and a civilian after he was stopped at a checkpoint in Dera Ismail Khan, a town near the Afghan border.
The blast is Pakistan's third since Friday and comes amid tight security for Shia Muslim ceremonies this week.
Elsewhere in the north-west, at least 11 people were hurt when a rocket was fired at a mosque in the town of Bannu.
The rocket landed near the building as Shia worshippers were leaving after prayers.
In the town of Kohat about 60km (35 miles) south of the North West Frontier Province (NWFP) capital, Peshawar, police said they had recovered explosives from under the stairs in a Shia mosque.
The blast in Dera Ismail Khan damaged nearby buildings and shattered windows.
Security officials say the suicide bomber was a teenager who blew himself up when police tried to search him at a road block.
"The attacker refused to be checked and detonated his explosives," Aslam Khattak, a senior police official in Dera Ismail Khan, told Reuters news agency.
Minority Shia Muslims were due to hold a procession nearby.
Pakistan's security forces are on alert for sectarian violence during the holy month of Muharram.
The festival of Ashura is on Tuesday, when Shias mark the death of the Prophet Muhammad's grandson Imam Hussein.
On Saturday, a suspected suicide bomber killed at least 13 people, two of them senior police officials, near a Shia gathering in the city of Peshawar.
A day earlier, police said a suicide bomber had killed himself and a security guard at a top hotel in Islamabad. There was no apparent sectarian motive.
Interior Minister Aftab Sherpao said on Monday that the authorities were still trying to establish who was behind the blasts.
The BBC's Barbara Plett in Islamabad says tensions are also high because of militant threats to take revenge for recent army operations in the tribal areas.
It is not clear who is behind the attacks, or whether they are linked.
But observers say many people in the government and outside are tempted to link the attacks to recent air strikes by Pakistani and Nato troops against pro-Taleban militants in the troubled Waziristan region.