At least three people were killed and 24 others injured when a bus carrying pilgrims was hit by a roadside blast in Akhtarabad town in Quetta, police and witnesses said Wednesday.

The bus, carrying at least 50 Shia pilgrims, was travelling from Iran to the city of Quetta in Balochistan when the attack happened near Qambrani Road.

The bus burst into flames after the intense blast. Panic gripped the area after the incident. Passersby and local residents shifted the victims to nearby hospitals on a self-help basis.

Emergency and rescue teams were dispatched to the blast site. An emergency has been declared at Bolan Medical Complex.

Security personnel were cordoning off the blast site to control the situation.

No group has admitted carrying out the attack but police say they believe the motive was sectarian.

Buses leave Quetta every day to carry pilgrims to the Shia holy sites in western Iran and parts of southern Iraq.

The area has been frequently been targeted in sectarian, suicide and other militant attacks in the past.