Islamabad, November 26 (RHC)-- At least one person has been killed and five others sustained injuries in a bomb explosion at a busy market in the southern Pakistani port city of Karachi. The casualties were caused after an improvised explosive device (IED) exploded near a bus terminal in Karachi's Lee Market on Wednesday.

The blast had earlier been reported by local Pakistani television channels as a gas cylinder explosion. The Wednesday attack came days after heavily armed assailants gunned down four paramilitary soldiers in the volatile city. According to reports, two gunmen on a motorcycle opened fire at a group of paramilitary forces guarding a mosque in Karachi's Baldia Ittehad Town on Friday.

Karachi, the capital of Pakistan's southern Sindh province, is home to numerous ethnic groups. It has been hit by clashes between rival ethnic and political factions in the past two and half decades.

Pakistani security forces have been engaged in massive anti-militant and crime operations in Karachi and come under attack by militants frequently. The Pakistani paramilitary troops have launched a crackdown on al-Qaeda militants in Karachi since September 2013. The attacks are usually blamed on militants linked to the Taliban in neighboring Afghanistan and also to al-Qaeda and other extremist groups.

Pakistan's army intensified its military operations after pro-Taliban elements killed over 150 people, most of them children, in an armed assault on a school in Peshawar in December 2014.

Pakistani officials say almost 3,000 pro-Taliban militants have been killed since the launch of the operation. This comes as Pakistan's spy agency Inter-Services Intelligence (ISI) is known as a staunch supporter of the Taliban.

Violence has been increasing in Pakistan following the 2001 U.S.-led invasion of neighboring Afghanistan under the pretext of terminating regional terrorism.