Syrian activists say the Islamic State group has seized more territory in the central province of Homs amid intense clashes with government forces.

The Britain-based Syrian Observatory says Wednesday's fighting killed at least 28 government troops and about 20 militants. It says hundreds were wounded.

The Islamic State has a presence in the eastern countryside of Homs and has been pushing west. Twitter accounts affiliated with IS say its fighters reported advances northwest of the city of Palmyra.

An activist based in Homs, Bebars al-Talawy, says the Islamic State seized a large government ammunition warehouse outside Palmyra and was bombing a nearby government-controlled airport.

Al-Talawy says the extremists took advantage of government redeployment on Tuesday to Idlib province where troops are fighting to regain territory seized by rebels.