By Can Sezer and Ayman al-Warfalli
ISTANBUL/BENGHAZI, Libya (Reuters) - Turkey and Russia urged Libya's warring parties on Wednesday to declare a ceasefire on Sunday as warring factions clashed and carried out air strikes in a conflict drawing increasing foreign involvement and concern.
Turkey backs Fayez al-Serraj's Tripoli-based, internationally recognized Government of National Accord (GNA) and has said it will send military advisers and possibly troops to reinforce its support, while Russian military contractors have been deployed alongside General Khalifa Haftar's eastern-based Libyan National Army (LNA).
After talks between their presidents, Tayyip Erdogan and Vladimir Putin, in Istanbul, Turkey and Russia called jointly for an end of hostilities, normalization of life in Tripoli and other cities, and U.N.-sponsored peace talks.
The conflict is undermining regional security and "triggering irregular migration, further spread of weapons, terrorism and other criminal activities including illicit trafficking," their statement said.
Any ceasefire deal will likely be hard to enforce after a recent escalation in fighting around Tripoli and Sirte, and given the fractious, loose nature of Libya's military alliances.
The United Nations has been leading efforts for months to pave the way for a truce and political negotiations in Libya, a major oil and gas producer, with few visible signs of progress.
The GNA said late on Wednesday it welcomed any "serious call" to return to political talks, without addressing the ceasefire call directly.
The United Nations said it welcomed recent ceasefire calls, including that from Turkey and Russia, and urged Libyan parties to respond positively.
Haftar's LNA took control of Sirte, a strategically important city in the center of Libya's Mediterranean coastline, in a rapid advance on Monday and is seeking to consolidate gains.
Since April, the LNA has also been waging a campaign to take the capital, Tripoli, about 370 km (230 miles) northwest of Sirte, where it is battling forces aligned with the GNA.
GNA forces said on Tuesday they had withdrawn from Sirte to avoid bloodshed. Those forces are mainly from the port of Misrata, 190 km (118 miles) east of Tripoli, and had controlled Sirte since driving Islamic State militants from the city in late 2016.
On Tuesday afternoon, clashes broke out around al-Washka, on the road between Sirte and Misrata, where LNA sources said nine of their men were killed in an evening drone attack.
On Wednesday, the LNA responded with air strikes near the Abu Grein checkpoint, close to al-Washka, where clashes were continuing, LNA military officials said.
Later, unusually heavy artillery bombardment could be heard around Mitiga airport in Tripoli, which was closed last week because of shelling and rocket fire.
PEACE PUSH UPENDED
Libya has been divided since 2014 into rival camps based in Tripoli and the east, each with its own set of institutions, and Haftar's offensive against Tripoli upended U.N. efforts to broker a political settlement.
The upheaval in Libya, where strongman Muammar Gaddafi's long rule was toppled in 2011, has in recent years disrupted the OPEC member state's oil production, fuelled migrant smuggling to Europe and given space to Islamist extremists.
Concerned regional powers have stepped up intervention, with the LNA also receiving support from the United Arab Emirates, Jordan and Egypt.
In Cairo, the foreign ministers of France, Egypt, Greece and Cyprus stressed their opposition to Turkey's decision on a troop deployment to Libya, and to a maritime deal Turkey struck with the GNA in November that Greece and Cyprus see as a threat to their natural gas drilling rights.
Serraj made a brief trip to Brussels on Wednesday to meet EU officials and Germany's foreign minister and was warned against allowing Turkish troops on Libyan soil or pursuing the maritime deal with Turkey.
The European Union, seeking to avoid being sidelined as Turkey and Russia jostle for influence in Libya, pressed Serraj to work for a ceasefire.
"Libya cannot become a second Syria and so we need rapidly to enter a political process, an agreement on an effective ceasefire and an arms embargo," said German Foreign Minister Heiko Maas. He added that he hoped a long-planned summit on Libya would be held in Berlin in the coming weeks.
Italian Prime Minister Giuseppe Conte held talks with Haftar in Rome on Wednesday. Conte had also been due to see Serraj later in the day, but the meeting was abruptly called off.
A government source said it appeared that Serraj had pulled out of the encounter after being wrongly informed the Italians wanted him to see Haftar during the trip.
(Reporting by Ayman al-Warfalli in Benghazi and Ahmed Elumami in Tripoli, Olesya Astakhova and Can Sezer in Istanbul, Giuseppe Fonte in Milan, Crispian Balmer in Rome and Aidan Lewis in Cairo; Writing by Aidan Lewis and Andrew Cawthorne; Editing by Mark Heinrich and Peter Cooney)