A bomb tore through a Pakistan election rally on Monday, killing four people and wounding 43 in the first attack in the northwestern tribal belt on a political party during the campaign.
The attack brings to 73 the number of people killed in violence against politicians and political parties since April 11, according to an AFP tally, ahead of Pakistan's historic elections on Saturday.
The explosion targeted the right-wing Jamiat Ulema-e-Islam (JUI), a religious party in the outgoing government coalition.
The bomb exploded in Kurram, one of the seven districts making up Pakistan's Taliban-infested tribal belt on the Afghan border.
"The death toll is now four with 43 people injured," said Doctor Najeeb Khan from the main hospital in Kurram tribal district.
"Some of the critically injured have been moved to Peshawar," he added, referring to the main city in the northwest.
Riaz Khan, the top administrative official in Kurram, told AFP the bomb was planted inside the building that was the venue for the rally of two national assembly candidates representing the JUI faction led by cleric Fazul-ur-Rehman.
One of the candidates, Munir Orakzai, escaped unhurt while the other, Ain u Din Shakir, was slightly injured, Khan said.
It was the first deadly attack on a political party in Pakistan's tribal belt since campaigning began for the polls, which will mark the country's first democratic transition of power after a civilian government has completed a full term in office.
Pakistan's interim Prime Minister Mir Hazar Khan Khoso strongly condemned the attack and said another national assembly candidate had been injured.
Repeated calls for candidates to be granted more security have failed to stop a wave of attacks, most of them claimed by the Pakistani Taliban.
There was no immediate claim of responsibility for the latest blast. The tribal belt is a stronghold of Islamist militants and Kurram has been dogged by sectarian violence between Pakistan's Sunni Muslim majority and Shiite minority.
The Pakistani Taliban have condemned the elections as unIslamic and directly threatened the main outgoing coalition parties, the PPP, the MQM and the ANP.
But Rehman and his JUI faction have been a mediator between the authorities and the insurgent group, which have been blamed for killing thousands of Pakistanis in a domestic insurgency over the last six years.
Elections have been postponed in three constituencies, in the southwestern province of Baluchistan, in Pakistan's biggest city of Karachi and in the southern city of Hyderabad, where candidates have been killed.