Islamabad, Nov 22 (IANS): Twenty people have died in Pakistan's Rawalpindi city when a powerful explosion ripped through a Shia procession, police said Thursday.

The attack took place around 11.40 p.m. Wednesday when a suicide bomber blew himself up among a crowd of worshippers, Rawalpindi Deputy Commissioner Saqib Zaffar said.

Over 1,500 Shia Muslims took part in the procession. Nearly 50 others were injured.

The police said about five kilograms of explosives were used in the attack. Seven grenades were also recovered from the scene of the blast, Xinhua reported.

The injured were shifted to various hospitals. Officials said the toll could rise as some of the injured, including women and children, were in critical condition.

Wednesday's blast took place hours after a twin-bomb explosion in Karachi targeting Shia Muslims left at least two people dead and 15 others.

Interior Minister Rehman Malik has ordered the administration to beef up security.