A Kurdish and Arab Syrian militia backed by the United States has captured the town of Karama as it prepares for an assault on the Islamic State stronghold of Raqqa that it expects to take place in early April, it said on Sunday.

The Syrian Democratic Forces (SDF) has trapped Raqqa in a shrinking pocket of territory on the northern bank of the Euphrates and has advanced toward it in a multi-pronged offensive over several months.