BEIRUT - Turkey carried out an airstrike in northern Syria on Tuesday near its border killing at least 11 people, including Syrian government soldiers, an opposition war monitor and a Kurdish media outlet said.

The attack happened just west of the northern town of Kobani and comes amid tensions in northern Syria between U.S.-backed Kurdish fighters and Turkey-backed opposition gunmen.

Syrian state media quoted an unnamed military official as saying that the Turkish airstrikes killed three soldiers and wounded six. The official said Syrian troops retaliated by targeting Turkish army positions and those of Turkey-backed opposition fighters.

The Britain-based Syrian Observatory, an opposition war monitor, said the Turkish airstrike killed 11 people, adding that it was not immediately clear if they were all Syrian soldiers. It said eight people were also wounded.

Hawar News, the news agency for the semi-autonomous Kurdish areas in Syria, reported that 16 Syrian soldiers were killed, while another Kurdish news agency, North Press Agency, said 22 soldiers were killed.

Discrepancies in casualty figures immediately after attacks are not uncommon in Syria.

Turkey's Defense Ministry said Tuesday that 13 suspected Kurdish militants were killed after Turkish artillery retaliated against a deadly attack on a Turkish border post near the town of Birecik in the border province of Sanliurfa. The ministry said operations in the region were continuing.

Provincial Governor Salih Ayhan told Turkey's state-run Anadolu Agency that a soldier was killed and four other soldiers were wounded in the attack on the Cicekalan border post early on Tuesday.

In a separate announcement on Twitter, the Defense Ministry said five other Kurdish militants were also killed by Turkish artillery systems. It said they were allegedly preparing for an attack on Turkish-controlled areas of northern Syria and had opened 'harassment fire' on the region.

Turkey has launched three major cross-border operations into Syria since 2016 and already controls some territories in the north.