QUETTA - A passenger bus plunged into a ravine in southwestern Pakistan on Sunday killing 20 people, a government official said.

The road crash also injured another 13 people aboard the bus that was travelling from garrison city of Rawalpindi to Quetta, the capital of southwestern Balochistan province, said Ijaz Jaffar, deputy commissioner of Sherani district.

The ravine is some 350 kilometres north of Quetta.

Poor road infrastructure and rash driving often cause deadly road crashes in Pakistan.

The province is home to several Chinese projects under an investment plan in which Beijing is seeking road and sea trade linkages with the world.

(Reporting by Gul Yousafzai; Writing by Asif Shahzad; Editing by Toby Chopra)