Forces from the provisional Libyan government have raided the Tripoli home of a family said to be key Gaddafi allies.
They arrested four brothers suspected of planning bomb attacks in the capital.
Neighbours joined in as government forces opened fire on the house using artillery and assault rifles.
Some reportedly wanted to exact vigilante justice on the brothers but were prevented from doing so.
Libya’s new rulers, still based in Benghazi, are locked in increasingly drawn-out battles to dislodge Gaddafi loyalists from several towns.
Fighters near the front line close to Sirte say they cannot defeat his forces there because they are not receiving enough ammunition. But after being pushed back at the weekend, they say they are again approaching the town’s eastern gate.
Residents fleeing Sirte said they had been living under a state of siege and had been prevented from leaving by Gaddafi loyalists.
At least five anti-Gaddafi fighters were killed in the latest fighting. Others met heavy resistance, 50 kilometres east of Sirte, and said they were unable to respond due to a lack of firepower.
Away from the battlefield, there was a boost for the interim government when the African Union said it was recognising the National Transitional Council, ending a long-standing relationship with Gaddafi.