At least four people were killed and 18 others injured in a bomb blast in Pakistan's southwest Sibi district on Sunday, officials said.

Anwar Khetran, district police officer (DPO), said that the some unknown militants exploded the bomb with a remote controlled device in Chakar Khan area of Sibi, a district located in the country's southwest Balochistan province.

The bomb disposal unit said that an estimated two to three kg of explosive materials fixed at a roadside parked motorbike were used in the blast.

Target of the blast has yet to be ascertained.

Several nearby shops and buildings were damaged in the blast.

The injured people have been shifted to Civil Hospital Sibi where at least three of them were reportedly in critical condition.

There was no immediate claim of responsibility for the blast.

Police cordoned off the area for investigations.

Both President Mamnoon Hussain and Prime Minister Nawaz Sharif condemned the blast and directed the hospital administration to provide best possible medical treatment to the injured people.