The head of the Pakistan Muslim League-N Sanaullah Zehri was on the campaign trail for the May 11 general election when the blast hit his convoy on Tuesday in Khuzdar district, 350 kilometres (220 miles) south of provincial capital Quetta.

"An improvised explosive device (IED) went off as Zehri, leading a convoy of more than 20 vehicles, left his home to campaign in Khuzdar," provincial home secretary Akbar Durrani said.

Zehri survived the assassination but his son, brother, nephew and their guard were all killed, officials said.

On Monday, April 15, gunmen killed two election campaigners for an independent candidate running in the lawless northwestern tribal regions, a day after a roadside bomb in the Swat valley killed a local leader of the Awami National Party (ANP).

“Mukarram Shah, was travelling to Mingora when his vehicle was targeted by an IED, around 12 km northeast of Mingora city,” said Gul Afzal Afridi the district police chief.

No group has claimed responsibility for the attacks, but police officials blame pro-Taliban terrorist groups who have carried out similar assaults in the past.

A roadside bomb attack had previously struck the northwestern town of Bannu on March 31, killing two people and wounding six others, including a member of the ANP identified as Adnan Wazir, who is a candidate for the Khyber Pakhtunkhwa provincial assembly.

Pakistan will go to the polls on May 11 to choose new national and provincial assemblies due to which the country has been experiencing increasing violence.

Thousands of Pakistanis have lost their lives in bombings and other terrorist attacks since October 2001, when Pakistan joined an alliance with the United States in its so-called war on terror.

Since late 2009, there has been a surge in terrorist attacks in Pakistan and thousands more have been displaced by the wave of violence and militancy sweeping across the country.