Police said a search was on to find the assailants (Representational)

A senior politician was shot dead along with his grandson and two security guards on Saturday in Pakistan's Balochistan province.

Balochistan National Party-Mengal (BNP-M) leader Amanullah Zehri was returning to his residence in the wee hours when his convoy was ambushed by unidentified gunmen in Khuzdar district, said Deputy Commissioner Major Muhammad.

"Zehri, his 14-year-old grandson Mardan Zehri and his two guards were killed on the spot," Muhammad said.

The deputy commissioner said the entire tehsil was sealed and search was on to find the assailants.

BNP-M chief Nawab Akhtar Mengal mourned the loss of lives.

"Another dark day for BNP and the people of Balochistan. This loss has deprived us all. I''m lost of words today (sic)," he said in a tweet.

On Friday, the brother of an Afghan Taliban leader Mullah Haibatullah was among five people killed when a powerful bomb ripped through a mosque inside a seminary during Friday prayers in Balochistan province.