Karachi: At least 5 militants and 4 people, including rangers and police personnel, were killed after the four-hour-long operation by the Law enforcement agencies in Pakistan's Karachi, weeks after the deadly attack in Peshawar's police line, Geo News reported.

Among 5 militants, three of them blew themselves up while two were gunned down in the shootout that took place on Friday, officials confirmed.

Meanwhile, 18 people were injured, officials confirmed to Geo News, the latest attack on security forces as terrorism grips the nation.

After the long-hour operation, the LEAs cleared the five-story office of the city's police chief.

The incident invited strong criticism from the top government officials, however, Defence Minister Khawaja Asif told Geo News that "condemnations are not enough" and strict action must be taken against militants.

The attack began at 7:10 pm, while police and Rangers personnel cleared the five-story building in phases, finally sweeping the entire office by around 10:46 pm.

Rangers and police teams have started a joint operation against the terrorists following the armed attack on the Karachi Police Office (KPO) - the Additional Inspector General (AIG) Office, reported ARY News.

The Rangers spokesperson said that the quick response force (QRF) of the paramilitary troops surrounded the KPO building and took their positions. An operation was started by Rangers and police to clear the KPO from terrorists.

The spokesperson added that the operation is being conducted on the reported presence of eight to 10 terrorists in the Karachi police chief's office.

A police officer, who did not want to be named, told Geo News that the attackers entered the office wearing police uniforms -- a similar move used in the Peshawar mosque suicide attack that claimed the lives of more than 80 people.

Meanwhile, seven people including Rangers police personnel have been injured, reported Geo News.

Police officials said that armed suspects -- whose total numbers are unknown at the moment -- fired several rounds at the head office -- located adjacent to the Saddar Police Station.

In view of the terrorists' attack, the Karachi Traffic Police blocked both sides of Shara-e-Faisal from Avari Hotel to Nursery.

Talking exclusively to Geo News, Interior Minister Rana Sanaullah said that there was a general security threat following the terror attack in Peshawar. "All the institutions are fully alert across the country," he added.

The security czar stressed the need for taking further steps to counter the fresh wave of terrorism.

"The police have said that the terrorists threw a grenade after parking the vehicle, and used that as a cover for entering the building," he revealed.

In a statement, Islamabad IG Akbar Nasir Khan confirmed that security is on high alert in the federal capital and all officers have been instructed to stay in their respective areas, reported Geo News.

"Checking of entry and exit routes and inside the city has been increased," he said, adding that officials have been directed to keep all important buildings and Red Zone on high alert.