Fighting has broken out in the heart of the Libyan capital for the first time in two months as revolutionary forces open fire at suspected snipers loyal to Muammar Gaddafi.
Anti-Gaddafi fighters converged on the Hay Nasr district of Tripoli's Abu Salim neighbourhood in pickups mounted with weapons and began setting up checkpoints.
Many opened fire at the buildings, fearing snipers were inside.
Assem al-Bashir, a fighter with Tripoli's Eagle Brigade, says the shooting began after a man was spotted raising the green flag that symbolised Gaddafi's ousted regime.
Booms echoed across the city in the first serious burst of violence in the capital since then-rebels seized control of the city in late August and forced Gaddafi into hiding.
Meanwhile revolutionary forces pounded Gaddafi supporters holed up in two neighbourhoods in Sirte with rocket and machine-gun fire but the loyalists showed no sign of giving up in the fugitive leader's home town.
Libya's new rulers have insisted Sirte's fall is imminent, and they expect to declare liberation this week. That could allow them to name a new interim government and set a timeline for holding elections within eight months.
But Gaddafi's forces have proven resilient, fighting back fiercely despite heavy shelling and Nato air strikes.
Former rebels control much of the battered coastal city after launching a major push a week ago, but they were still under intense sniper fire today.
Wounded fighters streamed into front line medical units, then were evacuated to field hospitals on the city's outskirts.
Pro-Gaddafi forces also maintain control over the desert town of Bani Walid.
Nato was conducting "intensive overwatch missions" around both areas, according to the British Ministry of Defence.
British warplanes struck three armed trucks belonging to former regime forces hidden beneath trees east of Bani Walid on Thursday, the ministry said.
"The vehicles were successfully engaged by our aircraft, using Paveway guided bombs, and destroyed," Maj Gen Nick Pope said in a statement.
Nato has called the continued resistance by Gaddafi forces in Sirte "surprising", as they appear to be losing the battle since revolutionary forces have the area surrounded.
Tanks and weapons-mounted vehicles from the revolutionary forces have kept up a steady barrage of fire into the small enclave known as District 2, where commanders believe several hundred remaining loyalists, possibly including high-ranking figures from the former regime, are hiding.
Thousands of civilians have fled the city to escape the violence.