* Libyan rebels enjoy fresh successes in West
* NATO drops leaflets, warns of helicopter attacks
* Rebels also advance towards eastern oil town Brega
* Tunisia aircraft fly after rockets land over border
(Adds Jufrah bombing, U.S. speaker)
By Youssef Boudlal and Matt Robinson
KIKLA/MISRATA, Libya, June 14 (Reuters) - Libyan rebels made fresh gains on the western front on Tuesday, pushing back forces loyal to leader Muammar Gaddafi in a string of clashes that brought them closer to the capital Tripoli.
Insurgents also sought to extend an advance in the east, setting their sights on the oil town of Brega in a bid to extend their control over the region, epicentre of the four-month rebellion against Gaddafi’s four-decade rule.
They seized the town of Kikla, 150 km (90 miles) southwest of Tripoli, after government troops fell back, and pushed several km (miles) west of their Misrata stronghold to the outskirts of government-held Zlitan, Reuters photographers said.
Pro-Gaddafi forces retreated about nine km (five miles) from Kikla and rebels were setting up defensive positions, they said.
In Brussels, NATO spokesman Wing Commander Mike Bracken said rebel forces were making steady advances in the west and the Berber highlands, and appeared to “control the ground from Wazin to Jadu and Zintan as well as the town of Yaffran.
“In the east ... there has been little movement from either side and no significant changes to the intensity of activity.”
The push to Kikla came after weeks of deadlock between the rag-tag army and government forces, though air strikes by NATO have taken their toll on Gaddafi’s better-equipped troops.
Rebels in the west said attacks on a Misrata oil refinery were not hampering supplies as first feared. A NATO leaflet drop warning of helicopter strikes prompted some rebels to retreat from their newly captured positions outside Zlitan.
“We came back because of the leaflets from NATO. I hope there is some coordination between the fighters and NATO. Gaddafi’s forces are far away. Is it logical that NATO has no idea we took those positions?” Mohammed Genei, 31, local commander told Reuters. “NATO dropped the leaflets right on us.”
A leaflet obtained by Reuters showed a picture of a helicopter and a burning tank. “When you see these helicopters, it means it is already too late for you,” it said in Arabic. “There is no place to hide. If you continue threatening civilians, you will be killed.”
A NATO official said the alliance did drop leaflets warning of the possibility of attack by helicopters, but said this was west of Misrata, and closer to Zlitan. However, even without the threat of NATO attack, the rebels said they would not attack Zlitan, citing tribal sensitivities. Instead they would wait for the local inhabitants to rise up.
Citing a rebel commander, the London Times newspaper said Gaddafi forces had hidden Grad rockets and ammunition in the Roman city of Leptis Magna, dating back to 200 BC.
The United Nation’s cultural body, UNESCO, called on all sides to ensure the protection of Libya’s “precious legacy.”
NATO reported skirmishes around Brega and Ajdabiyah but said the east of Libya was relatively quiet. It said there were reports of a rebel offensive on Zawiyah, an oil-producing port 30 km (20 miles) west of Tripoli.
“This area appears to be a hotspot for pro- and anti-Gaddafi clashes,” Bracken told the briefing in Brussels.
But a Zawiyah resident, who could only be named as Mohamed, told Reuters by phone on Tuesday that it had since gone quiet, with neither side having advanced much since the skirmish.
The main highway west from Tripoli to Tunisia, which had been closed because of the fighting, reopened.
NATO said it struck armoured vehicles and rocket launchers east of Tripoli on Tuesday and vehicles in Misrata on Monday.
State television reported late on Tuesday the alliance had bombed Al Jufrah in the centre of the country for a second consecutive day.
South African President Jacob Zuma accused NATO on Tuesday of abusing a U.N. resolution authorising it to protect Libyan civilians in order to pursue “regime change ... assassinations and foreign military occupation”.
U.S. Secretary of State Hillary Clinton urged African leaders on Monday to abandon Gaddafi, who has styled himself the African “king of kings” and over the years won support from many African states in exchange for financial help.
Liberia heeded that call on Tuesday severing diplomatic ties with Gaddafi’s government, joining Senegal and Mauritania, who have already distanced themselves from the Libyan leader.
NATO defence chiefs met in Belgrade to discuss the mission, after U.S. Defense Secretary Robert Gates accused some European allies of failing to pull their weight.
A senior NATO commander appeared to raise questions about the alliance’s ability to intervene in Libya long-term.
“The Libyan crisis came as a surprise to, I guess, everybody ... We are conducting this operation with all the means we have, and the best we can. If the operation were to last long, of course, the resource issue will become critical,” General Stephane Abrial told the NATO conference in Belgrade.
Republican U.S. House Speaker John Boehner told President Barack Obama on Tuesday the administration would be in violation of the country’s 1973 War Powers Resolution this Sunday unless Libyan operations end by then or Congress authorises them.
The resolution prohibits U.S. armed forces from being involved in military actions for more than 60 days without congressional authorization.
Tunisia flew an F-5 warplane and a helicopter along its border with Libya, fanning tensions, after Libyan troops fired several rockets into Tunisia.
The explosions, close to rebel territory along the border in Libya’s Western Mountains, caused no damage or injuries.
A Reuters journalist in the village of Ryayna, 15 km east of Zintan in the insurgent-held Western Mountains southwest of Tripoli, said Gaddafi’s forces had been pushed back.
The rebels have been trying unsuccessfully to seize Ryayna for several weeks. They said two of their fighters were killed. (Additional reporting by Matt Robinson in Misrata, Tarek Amara in Tunis, Nick Carey in Tripoli, Mohammed Abbas in London, Jaksa Skekic in Belgrade, Hamid Ould Ahmed in Algiers, David Brunnstrom in Brussels, Souhail Karam and John Irish in Rabat; Writing by Tim Cocks and John Irish; Editing by Andrew Heavens)