At least five blasts have rocked the Libyan capital after NATO planes flew over Tripoli, AFP witnessed amid rebel reports that mortar shells and rockets also rained on the coastal city of Misrata.
Three blasts could be heard from the city centre around 11pm (0700 Friday AEST), followed by two others a few minutes later.
Witnesses told AFP they saw smoke rising from the Ain Zara district in the southeast, which has been regularly targeted by NATO war planes.
On Thursday, rebels and forces loyal to Muammar Gaddafi battled over control of a key border post, fighting on
both sides of the Libya-Tunisia frontier, sources said.
Rebels recaptured the Dehiba border post after heavy fighting killed eight soldiers of forces loyal to Gaddafi, just hours after the strongman's troops took control of the crossing.
On the Libyan side of the border, the rival camps exchanged artillery fire in the early evening, causing panic among civilians, a witness told AFP.
Several ambulances came from Tunisia into Libya to evacuate the wounded.
According to a security source, five pro-Gaddafi fighters were wounded in the clashes and taken to a hospital in Tataouine in Tunisia.
A senior Tunisian military officer described the situation as "extremely tense".
Earlier in the day, Gaddafi's fighters had for a few hours taken control of Dehiba which rebels seized a week ago, causing the insurgents to flee into Tunisia pursued by their enemies for about one kilometre.
Some of them managed to return to Libya while others, as well as Libyan soldiers, were arrested by Tunisian forces, said a witness on the border who asked not to be named.
"The situation is very confused, and there is fighting on both sides of the border" at Dehiba, a military official told AFP.
A witness said Tunisian troops had arrested fighters on both sides of the conflict but this could not be confirmed independently or by Tunisian officials.
The insurgents' success in capturing Dehiba on April 21 resulted in thousands of Libyans crossing the border into Tunisia in anticipation of a counter attack as forces loyal to Gaddafi started amassing in the area.
