AFP - The Turkish army on Monday said 31 soldiers had been killed since Ankara launched its offensive against a Kurdish militia in Syria last month.

Another 143 Turkish soldiers were wounded in the operation dubbed "Olive Branch" which began on January 20 against the Syrian Kurdish People's Protection Units (YPG) militia in the western region of Afrin, a statement said.

While the United States has given armed support to the YPG against the Islamic State group in Syria, Turkey says the militia is a "terrorist" offshoot of the outlawed Kurdistan Workers' Party (PKK).

The PKK, proscribed as a terrorist organisation by Ankara and its Western allies, has waged a three-decade insurgency against the Turkish state.

Turkey has been supporting Syrian rebels with ground troops and air strikes during the operation which Ankara has threatened to extend eastwards towards other YPG-held towns.

Turkey suffered its bloodiest day on Saturday when 11 military personnel were killed, including two after a helicopter taking part in the offensive was downed.

Some 1,369 "terrorists" had been neutralised during the operation, the army said, referring to those killed but also those captured or wounded.

It was not immediately possible to verify this figure.

But according to the Britain-based Syrian Observatory for Human Rights, 152 YPG fighters and 165 Turkey-backed Syrian rebels have died in the operation.

The Observatory said at least 74 civilians have been killed in the operation so far.

Turkey has repeatedly insisted it is taking all the necessary precautions to avoid harming civilians and says there have been no civilian casualties to date.

At least seven civilians have been killed in Turkish border towns after rockets were sent from Syria in attacks Ankara blames on the YPG.