Updated

Syrian activists say rebels have seized key security buildings in the northern city of Raqqa where opposition fighters had been battling the last pockets of resistance by government troops.

The Britain-based Syrian Observatory for Human Rights says the strategic city on the Euphrates is now completely under rebel control.

If confirmed, it would be the first major city to fall completely into rebel hand since Syria's conflict began nearly two years ago. It also would consolidate recent rebel gains in the towns along the river, which runs from Turkey to Iraq.

The Observatory and other activists said rebels seized control of the Military Intelligence headquarters and another security building in Raqqa on Wednesday after three days of fighting, and freed scores of detainees inside.