A fighter plane was shot down and there were mortar and artillery attacks on Saturday morning in the rebel-controlled Libyan city of Benghazi, Al Jazeera reported.
It was, however, not known to which side the plane belonged because Libyan officials said rebels were using helicopters and fighter jets to bomb the forces of embattled leader Muammar Gaddafi.
"Gangs of Al Qaeda attacked units of the Libyan Armed forces stationed to the west of Benghazi," the official Jana news agency cited a government statement as saying.
The statement said rebels were using a helicopter and a fighter jet to bomb the Libyan armed forces in ‘blatant violation’ of the no-fly zone imposed by the UN Security Council.
Al Jazeera reported mortar and artillery attacks on streets in central Benghazi.
Pro-Gaddafi forces have entered the suburbs of the city, it said.
"The explosions started about 2.00am Gaddafi's forces are advancing, we hear they're 20 km from Benghazi. It's land-based fire. We saw one aircraft," Faraj Ali, a resident, said.
Earlier, media reported that a plane bombed an area South-West of Libya's rebel stronghold of Benghazi and two columns of smoke were seen rising from the targeted zone.
The sound of the aircraft could be heard from the centre of the city, where explosions could be heard overnight.
The Libyan Government and rebels fighting strongman Muammer Gaddafi's regime accuse each other of breaching a ceasefire announced by Tripoli following a UN resolution to impose a no-fly zone over the war-torn nation.
US President Barack Obama has delivered a blunt ultimatum to Gaddafi threatening military action if he ignored non-negotiable UN demands for a ceasefire and a retreat from rebel bastions.
Washington also accused the Gaddafi regime of violating the truce.
France is due to host later on Saturday what it said would be a ‘decisive’ summit with the European Union, Arab League and African Union, as well as UN chief Ban Ki-moon, on taking UN-sanctioned military action in Libya.
France's Ambassador to the UN, Gerard Araud, said he expected military intervention within hours of the summit.