Activists say an al-Qaida-linked group has pushed out rival rebels to regain full control of a provincial capital in northeastern Syria.

The Britain-based Syrian Observatory for Human Rights says the Islamic State of Iraq and the Levant expelled the last of its rebel opponents from the city of Raqqa on Tuesday after several days of fighting. The city is the only provincial capital in opposition hands.

Observatory director Rami Abdurrahman says the Islamic State is now in control of most of Raqqa province after fending off a challenge over the past 12 days from an array of moderate and ultraconservative rebel brigades.

The rebel infighting is the most serious among opponents of President Bashar Assad since the Syrian conflict began in March 2011.