BAGHOUZ, Syria (Reuters) - Falling bombs raised smoke over Islamic State's last enclave in east Syria on Sunday, obscuring the huddle of vehicles and makeshift shelters to which the group's self-declared "caliphate" has been reduced.

Air strikes and artillery began hitting the area and smoke billowed overhead late in the afternoon as U.S.-backed forces resumed their weeks-long attack, a Reuters reporter said.

After dark, a Kurdish TV channel broadcast live footage showing fires raging and the swift glow of rockets pounding into the enclave accompanied by the sound of intense gunfire.

During an earlier lull in fighting, tiny figures of people still inside were clearly visible walking among hundreds of trucks, cars and minibuses clustered around a few concrete buildings by the bank of the Euphrates.

It is all that remains to Islamic State in the heartland of the territory it seized in 2014, taking advantage of chaos in Iraq and Syria to grab about a third of both countries and eradicating the border between them.

However, the group's leader Abu Bakr al-Baghdadi is still at large and regional officials believe it will remain a threat after it has lost all its land.

The enclave is in Baghouz, a handful of hamlets in farmland next to the river along the Iraqi border. Despite its tiny size, more than 60,000 people have fled it in the past two months, said the besieging Syrian Democratic Forces (SDF) militia.

Nearly half of them were surrendering Islamic State supporters, mostly family members of jihadist fighters, though 5,000 armed militants also gave themselves up, said SDF spokesman Kino Gabriel.

Another 34,000 civilians were evacuated. Former residents from the region say many of the civilians who left the Baghouz area in recent weeks were Iraqi Sunnis with close tribal ties on the other side of the border in Deir al-Zor, a Sunni heartland.

They sought sanctuary in Syria for fear of reprisals by the Iraqi Hashd al Shaabi, the Iranian-backed Shi'ite militias in Iraq, the former residents said.

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How Islamic State lost Syria: https://tmsnrt.rs/2T8GFfC

AERIAL BOMBING

Another SDF spokesman, Mustafa Bali, told Reuters only about 100 militants and their families had surrendered overnight in the spot where hardline insurgents have been mounting a desperate last-stand defense.

"We had expected the surrender of a large number of terrorists and their families but only a small group came out," Bali said.

On Friday suicide blasts targeted some of the people leaving Baghouz and surrendering to the SDF.

The SDF said 1,306 "terrorists" had been killed alongside many who were injured in the military campaign that began on Jan. 9, while 82 SDF fighters had been killed and 61 injured.

The SDF said another 520 militants had been captured in special operations in the last Islamic State bastion.

Former residents say hundreds of civilians have been killed in months of heavy aerial bombing by the coalition that have razed many of the hamlets in the area along the Iraqi border.

The coalition says it take great care to avoid killing civilians and investigates reports that it has done so.

The SDF has mostly transferred the tens of thousands who have fled Islamic State's shrinking territory in recent months to a camp at al-Hol in the northeast.

A senior International Committee of the Red Cross (ICRC) official said last Monday an estimated 20,000 Iraqi women and children in the camp were expected to be sent home within weeks or months.

The United Nations says the camp now holds around 67,000 people, 90 percent of them women and children - well beyond its capacity. Camp workers say they do not have enough tents, food or medicine.

(Reporting by a Reuters journalist in Baghouz, Writing by Suleiman Al-Khalidi and Angus McDowall; Additional reporting by Rodi Said; Editing by Toby Chopra, Ros Russell, William Maclean, Gareth Jones)