Tunisian security forces have killed two militants and arrested two others with officials stating that they were linked to recent assassinations of opposition politicians.

The killings and arrests came during an operation in a northern suburb of the capital, Tunis, by the anti-terrorist squad on Monday after intense gun battle, a source with the Tunisian Interior Ministry said.

The two men arrested, Mohamed Khiari and Mohamed Aouadi, are leaders of the military wing of the Salafist extremist group, Ansar al-Sharia, and are implicated in the assassination of opposition lawmakers, Chokri Belaid and Mohamed Brahmi, the source added.

Last month, Tunisian Prime Minister Ali Larayedh, accused the Ansar al-Sharia, of carrying out the worst "terrorist" attacks since the 2011 revolution that overthrew former dictator Zine El Abidine Ben Ali.

Brahmi’s assassination on July 25 triggered widespread anti-government rallies nationwide. The slain official held a seat in the assembly tasked with writing the new constitution.

Government opponents blamed Larayedh's coalition government for failing to counter the militants behind the killings and called for the formation of a non-partisan national unity government. The ruling Ennahda party, however, rejected the call.

Tunisia, the birthplace of pro-democracy protests across North Africa and the Middle East, is struggling with a democratic changeover after the overthrow of its dictator.