At least nine people were killed and 42 others wounded in an explosion on a congested road in the central Pakistani city of Multan, police say.

The blast came when a motorcycle hit an auto rickshaw that police believe was carrying some kind of explosive material while travelling on the city's Vehari Road.

"At least nine people were killed and more than 40 were wounded," Multan police chief Azhar Ikram said, adding that the rickshaw had exploded on impact.

Ashiq Malik, chief of Nishtar Hospital, confirmed the death toll and said 42 others were wounded.

The doctor said 15 people were discharged after their wounds were dressed, while 27 were admitted to hospital.

Mr Ikram said police initially thought the Compress Natural Gas (CNG) cylinder installed in the rickshaw had detonated, but that bomb disposal staff later found traces of explosive material.

He said police had launched an investigation into the incident and were trying to identify the passengers in the rickshaw in an effort to discover where the explosives had come from and why they were being transported.

The southern parts of Punjab, the state where the city of 1.1 million people is located, are rife with sectarian militants allied to Taliban.

In the past year Pakistani authorities have cracked down on the myriad insurgent groups that have plagued the country for a decade.

The offensive intensified after Taliban gunmen slaughtered more than 130 children at a school in the northwest of the country in December last year.

AFP