Islamic State fighters have pushed into the Syrian town of Palmyra, home to famed 2,000-year-old ruins.
The Syrian Observatory for Human Rights and activist Bebares al-Talawy said the militants were clashing with government troops in the northern part of the town. The Unesco world heritage site is south west of Palmyra.
A video circulated on social media shows a man raising a black IS flag on a building allegedly in northern Palmyra.
The extremists have seized a gas field north east of Palmyra and nearby villages.
Palmyra is one of the most famous world heritage sites, and before the civil war thousands of tourists came to see its Roman-era colonnades. The IS offensive began on Thursday.