ISLAMABAD, July 16 (Xinhua) -- The death toll in a suicide bombing that targeted an election campaign rally in Mastung area of Pakistan's southwest Balochistan province on Friday rose to 149, local media and officials said on Monday.

Confirming the death toll, Qaim Lashari, the deputy commissioner for Mastung district, said at least 186 people also got injured in the blast, making it one of the deadliest attacks in the country's history.

The deceased include nine children aged between six and 11, said Lashari, adding that 70 people are still under treatment at hospital, with five in a critical condition.

Explaining the rise in the toll, Lashari said the bodies of 21 victims were never brought to the hospital but instead buried by their bereaved families and have been counted only now.

The target of the attack, which took place on Friday in the restive province of Baluchistan, was political leader Nawabzada Siraj Raisani, who lost his life in the attack, said the official.

Authorities said the suicide bomber detonated his explosives-laden jacket in the middle of a compound where the political meeting attended by over 1,000 people was taking place in the Darengarh area of Mastung.

Terrorist group of Islamic State claimed the Mastung attack on its website.

It was the second deadliest attack in Pakistan's history after the Karsaz bombing in 2007 in which over 160 people were killed when former Prime Minister Benazir Bhutto's convoy was targeted by terrorists in the country's southern Karachi city.

The death toll of the army school attack, claimed by the banned Tehreek-e-Taliban in 2014, was 147, according to government officials.

The Mastung bombing was the latest and deadliest of a string of attacks targeting politically active persons who are busy in holding public meetings and addressing gatherings ahead of general elections to be held in the country on July 25.

The latest attacks left about 171 people killed and over 200 injured during the last five days.

The caretaker government on Sunday has announced one-day mourning nationwide to pay respect to lives lost in the recent spate of terror attacks in the country.

Friday's attack has widely been condemned in Pakistan with President Mamnoon Hussain, caretaker Prime Minister Nasir-ul-Mulk, army chief Gen Qamar Javed Bajwa, Balochistan chief minister and others terming it a "cowardly act."