A spokesman for Iraq's Shiite militias says an operation launched to retake the western Anbar province from the Islamic State (ISIS) will "not last for a long time" and that Iraqi forces have surrounded the provincial capital, Ramadi, from three sides.

Ahmed al-Assadi, who is also a member of parliament, told reporters Tuesday that new weapons are being used in the battle "that will surprise the enemy."

Earlier on Tuesday, Iraqi state TV announced a major operation to retake Anbar, but it did not provide further details.

The government has called on Shiite militias to help the army retake the Sunni province, raising concerns the offensive could heighten sectarian tensions.

ISIS began seizing large parts of Anbar province in early 2014 and captured its capital, Ramadi, earlier this month. The fall of Ramadi marked a major defeat for Iraqi forces, which had been making steady progress against the extremists over the past year with the help of U.S.-led airstrikes.