The death toll in a suicide bombing at an election rally in northwestern Pakistan rose to 20 Wednesday as Taliban militants claimed responsibility, officials said, in the first major attack ahead of July 25 polls.
A local leader of the Awami National Party (ANP), Haroon Bilour, was among those killed in the attack in the city of Peshawar late Tuesday, officials have confirmed.
The party has been targeted by Islamist militants in the past over its vocal opposition to extremist groups like the Taliban.
The bombing came hours after the Pakistan military spokesman said there were security threats ahead of national elections.
"The death toll has risen to 20 and 63 others were wounded, out of whom 35 are still admitted in two Peshawar hospitals," Peshawar police chief Qazi Jameel told AFP.
Peshawar hospital official Zulfiqar Babakhel confirmed the updated death toll.
Bomb disposal chief Shafqat Malik told AFP that the suicide bomber -- who he said was around 16 years old -- had eight kilogrammes of explosives and three kilogrammes of pellets, ball bearings and other shrapnel on his body.
Peshawar lawyers went on strike on Wednesday to protest and mourn the death of Haroon, who was also a barrister. Local traders also announced a strike and mourners thronged to Bilour's residence to offer condolences.
Bilour was one of the ANP's election candidates and belonged to an influential political family in the Khyber-Pakhtunkhwa province, of which Peshawar is the capital.
His father Bashir Bilour, one of the ANP's top leaders, was also killed by a suicide bomber in 2012.
Police said the bomber struck when Bilour was about to address some 200 supporters.
Mohammad Khorasani, spokesman for the Tehreek-e-Taliban Pakistan militant group, claimed the responsibility for the attack.
"Tehreek-e-Taliban Pakistan's mujahid (holy fighter) Abdul Karim last night carried out a suicide attack on important ANP leader Haroon Bilour in which he has been killed," Khorasani said in a statement.
He said the militants "have already declared a war" on the ANP and called on the public to keep away from them, "or you will be responsible for your own loss".
Peshawar city is considered a gateway to Pakistan's troubled semi-autonomous tribal regions, where many militant groups -- including al Qaeda -- operated until the government launched operations to oust them.
Militants have targeted politicians, religious gatherings, security forces and even schools in Peshawar.
But security across Pakistan, including in Peshawar, has dramatically improved since government and military operations in recent years.
Analysts warn however that Pakistan has yet to tackle the root causes of extremism.