Updated

Russia says its air force has helped Syrian troops repulse an Islamic State attack on the historic town of Palmyra.

The Russian Defense Ministry said Sunday that it carried out 64 airstrikes overnight that killed 300 IS militants and destroyed the extremists' vehicles and artillery.

Palmyra is home to towering 2,000-year-old ruins and was a major tourist attraction before the civil war broke out in 2011. IS seized the town last year and held it for 10 months before being driven out by Russian-backed Syrian forces in March.

The militants have advanced on Palmyra in recent days, with reports of heavy fighting within the town itself. Syria's army has been largely focused on the northern city of Aleppo, where it is waging a major offensive against Syrian rebels.