Karachi, 30 October (AKI/DAWN) - Security has been stepped up across the southern port city of Karachi after police received "credible" intelligence reports of possible terrorist attacks in the city on Friday. Security barriers have been set-up across the metropolis, where police and armed forces remained on high alert .

According to police, an extensive campaign has been launched to identify suspects and suspicious activities in the city during the past 24 hours. Meanwhile over 250 suspects have been detained from various city areas during overnight raids.

Police sources told Pakistani daily Dawn that most of the detainees are Afghan nationals who were living in Karachi illegally. They added that spot-checks have been intensified following "credible" security threats. Sniffer-dogs have also been placed at over a dozen sensitive locations, police said without specifying which these were.

Police sources also said that "appropriate arrangements" have been made at all mosques, and places of worship, especially during Friday prayers.

Police also said last week they had foiled a "major" terror plot in Karachi.

Militants have in recent weeks carried out a series of deadly attacks in Pakistan that have killed hundreds of people.

Pakistan's excise and taxation Minister Sardarzada Rustam Khan Jamali was assassinated in Karachi in July.