By Humeyra Pamuk and Oliver Holmes

MURSITPINAR Turkey/BEIRUT (Reuters) - U.S.-led coalition jets pounded suspected Islamic State targets at least six times in the besieged Syrian town of Kobani on Saturday after the fiercest shelling in days by the insurgents shook the town's center and hit border areas within Turkey.

Shelling continued after the strikes hit the center of Kobani. Several mortars fell inside Turkey near the border gate, called Mursitpinar, according to witnesses.

Islamic State militants have battled Kurdish fighters for a month to take control of Kobani and consolidate a 60 mile (95 km) stretch of land they control along the Turkish border, but stepped-up air strikes in recent days have helped Kurds fend off the advance.

The coalition has been bombing Islamic State targets in Iraq since August and extended the campaign to Syria in September after the Islamic State, a group that espouses a rigid interpretation of Islam and initially focused on fighting Syrian President Bashar al-Assad's forces, made huge territorial gains.

NATO member Turkey is a somewhat reluctant member of the coalition, insisting it must also confront Assad to end a civil war that has killed some 200,000 civilians since March 2011.

On Saturday, the Britain-based Syrian Observatory for Human Rights said U.S-led forces bombing Islamic State in Syria killed 10 civilians in two separate air strikes.

But U.S. Central Command said there was no evidence to back up the report. Its forces use mitigation measures to reduce the potential for civilian casualties, a spokesman said.

Reuters cannot independently confirm the reports due to security restrictions.

'CUT OFF'

In Kobani, a commander for the YPG, the Syrian Kurdish militia defending Kobani, who would only gave her code name Dicle, said Islamic State's renewed attacks were aimed at severing the town's last link with Turkey.

"They want to cut off Kobani's connection with the rest of the world," she told Reuters by telephone. "Turkey is not allowing in fighters or weapons, but they send aid at Mursitpinar. The Islamic State wants to destroy this gate so that we will be completely trapped here."

Story continues

Turkey has refused to rearm beleaguered Kurdish fighters, who complain they are at huge disadvantage in the face of Islamic State's weaponry, many of it seized from the Iraqi military when it took the city of Mosul in June.

Turkey views the YPG with suspicion for its long-standing links with the Kurdistan Workers Party (PKK), which has waged a 30-year armed campaign for self-rule in Turkey.

President Tayyip Erdogan said earlier this month the PKK was no better than the Islamic State in his view.

This stance sparked outrage among Turkey's own Kurds, who make up about 20 percent of the population. Riots in several cities earlier this month killed more than 35 people.

INTENSE SHELLING

The Syrian Observatory said the Islamic State had launched at least 21 mortar attacks on Saturday close to the border.

Abdulrahman Gok, a journalist inside Kobani, said by telephone said the fighting was the worst in two days. "In the past hour, the shelling has intensified. They are firing almost one every two minutes," he said, adding that the insurgents were aiming at the east side of town towards the Mursitpinar gate.

A cloud of black smoke towered over the center of Kobani following the latest air strike as the roar of fighter jets could be heard from a blue sky. Gunfire popped in the west and center of town.

Elsewhere in Syria, government forces shelled neighborhoods in Damascus, the southern province of Deraa and the central province of Homs, opposition activists said.

Army helicopters were dropping improvised barrel bombs on the town of Khan Sheikhoun, in northwest Idlib province, which also borders Turkey, they said.

Islamic State supporters circulated what they said was a nine-second video clip of a fighter jet said to be flown by Islamic State militants.

The Observatory reported that Iraqi pilots who have joined Islamic State in Syria were training members of the group to fly in three captured fighter jets over the captured al-Jarrah military airport east of Aleppo.

U.S. Central Command said on Friday that it was not aware of Islamic State flying jets in Syria. Reuters could not confirm the authenticity of the footage, which showed a jet flying at low altitude.

Meanwhile, the United Nations said the Lebanese government has cut back sharply on the number of Syrian refugees it is allowing into the country. The country's Social Affairs Minister Rashid Derbas said in comments published a newspaper: "Lebanon is no longer officially receiving any Syrian refugees," except with those with pressing humanitarian needs.

Lebanon has the highest per capita concentration of refugees in the world, with one in four residents a refugee, many of them living in the poorest areas, and the government has said it cannot cope with the more than a million Syrians and has asked for funds to help look after them.

Turkey hosts about 1.5 million Syrian refugees, including almost 200,000 Syrian Kurds from Kobani.

Amid the escalated fighting, Turkish trucks could be seen carrying about two dozen Kurdish refugees away from the border.

Several hundred people are still sheltering in a minefield to the west of Kobani in order to stay with their vehicles and farm animals, which are not allowed in Turkey.

(Additional reporting by Hamdi Istanbullu, writing by Ayla Jean Yackley, editing by Rosalind Russell)