TUNIS/ZAWIYAH, Libya - Rebels battled for towns on either side of the besieged Libyan capital Tripoli on Saturday, and fighting spilled across the border into Tunisia, where Libyan infiltrators clashed with Tunisian troops.RELATED:Libya rebels fight Gaddafi for vital oil refineriesUS says "Gaddafi's days are numbered"
Tunisian security sources said their forces had intercepted Libyan men in vehicles with weapons and fought them through the night in the desert. They reported several casualties.
The six-month-old war in Libya came close to the frontier this week after rebels suddenly seized the coastal city of Zawiyah just 50 km west of Tripoli, surrounding the capital and severing its supply routes.
Gaddafi's forces west of Zawiyah and near the Tunisian border have been effectively encircled and cut off from their own supply lines. Tunisia has beefed up its army presence in the border area.
Residents of the southern Tunisian desert town of Douz told Reuters by telephone that helicopters were swooping overhead and troops had been summoned from nearby towns to subdue the infiltrators, who rode in vehicles without number plates.
The Tunisian security sources did not say whether the armed men were rebels or supporters of Gaddafi. Residents said they believed they were Gaddafi supporters.
Tunisian officials also said a Tunisian army helicopter had crashed because of mechanical problems in the border area, killing the pilot and co-pilot.The pending siege of Tripoli?
The siege of Tripoli and the prospect of a battle for the capital have added urgency to the question of Gaddafi's fate. The leader has repeatedly vowed never to leave the country. Rebels say they will not stop fighting until he is gone.
Representatives of the two sides held talks early this week in a Tunisian resort, attended by a former French prime minister, but announced no breakthrough. The severing of the road link between Tripoli and Tunisia makes further talks difficult.
A Tunisian official source said Libya's top oil official, Omran Abukraa, had arrived in Tunisia after deciding not to return to Tripoli from a trip to Italy.
If confirmed it would be the third apparent defection of a senior Gaddafi associate this week. A senior security official arrived in Rome on Monday and rebels said on Friday that Gaddafi's estranged former deputy Abdel Salam Jalloud had joined their side.
Mortar and rocket rounds crashed into the center of Zawiyah on Saturday. Shells struck the central hospital around dawn, blasting holes in the walls.
In the central square, residents were burning and stamping on a green Gaddafi flag. "Gaddafi is finished. Civilians are starting to come back to the cities. Libya is finally free," said one, who gave his name as Abu Khaled.
In a nearby alley, residents had gathered to stare at the bodies of two
Gaddafi soldiers lying in the street. Gunfire and explosions could be
heard in the distance.
Rebels said the main Gaddafi force had retreated about 10 km east to the town of Jaddayim and was shelling Zawiyah from there.
East of the capital, where fighting has been bloodier and rebel advances
far slower, opposition forces fought street battles in the city of
Zlitan but suffered heavy casualties, a Reuters reporter said on Friday.
A rebel spokesman said 32 rebel fighters were killed and 150 wounded.
Gaddafi's spokesman Moussa Ibrahim said late on Friday the government's military held the upper hand in both Zawiyah and Zlitan.
The sudden imposition of a siege around Tripoli has trapped its
residents behind the front line and cut it off from fuel and food. The
International Organization for Migration said on Friday it would
organize a rescue operation to evacuate thousands of foreign workers,
probably by sea.