ISTANBUL (Reuters) - Turkish-backed rebel forces in northern Syria have gained control of three areas in the last 24 hours as they press a two-month-old operation to drive Islamic State and Kurdish militia forces from the border, the Turkish army said on Tuesday.

It said Turkish howitzers shelled 72 Islamic State and 15 Kurdish YPG militia targets as part of the “Euphrates Shield” operation launched in August, which has also been backed by Turkish warplanes and tanks.

With ground and air fire support the Syrian rebels “largely secured control” over the areas of Tuways, Al Gharz and Tlatinah south of Akhtarin, the military statement said, adding five rebels were killed and 28 wounded in the latest clashes.

The assault appeared to mark the first advance by the rebels in several days, widening the territory which they have seized since the start of the operation to 1,280 square kilometers (494 square miles), according to the statement.

Aircraft from the U.S.-led coalition carried out four air strikes, killing four Islamic State fighters and destroying two buildings and two vehicles, it said.

Turkish-backed rebels fighting under the banner of the Free Syrian Army crossed into northern Syria on Aug. 24 and took control of the border town of Jarablus from Islamic State largely unopposed.

President Tayyip Erdogan said on Saturday the Turkish-backed forces would press on to the Islamic State-held town of al-Bab, around 15 km (9 miles) from their current location.

The Syrian military said last week the presence of Turkish troops on Syrian soil was unacceptable and a “dangerous escalation and flagrant breach of Syria’s sovereignty”.