IS militants seized full control of the ancient city of Palmyra in central Syria on late Wednesday, RIA Novosti reported referring to a local source.
Syrian government forces and their allied militias withdrew from Palmyra to avoid fighting in the historic part of the city, according to the source.
The majority of the city's civilian population had been evacuated before the withdrawal, it added.
On May.20, the Syrian Observatory for Human Rights (SOHR) said the jihadists had seized almost all of the city. This information was not officially confirmed by local authorities.
Palmyra has been an epicentre of fierce fighting between IS militants and Syrian troops for about a week.
Palmyra is one of the most important cultural sites in the Middle East and is included in the UNESCO world heritage list.
According to SOHR, about 300 people were killed in the clashes between the Syrian government forces and IS while the militants were approaching the ancient city.
Vast territories in Syria, which has been in the state of civil war since 2011, are currently controlled by IS. The militants captured parts of Syria in 2012, and in 2014 expanded into Iraq. The militants have declared a caliphate on territories under their control.
A number of IS cells are also known to operate in Libya, Yemen and other territories in the Middle East and North Africa.