The soldier was shot by members of the Kurdish People's Protection Units (YPG) militia from the nearby city of Tal Rifaat, east of Afrin, the ministry said in a statement.

The Turkish army responded with "heavy fire" against YPG targets, the ministry added.

The city of Afrin was captured in March this year from the US-backed militia by Turkish armed forces and Syrian rebels supported by Ankara.

Ankara says the YPG is a "terrorist offshoot" of the outlawed Kurdistan Workers' Party (PKK), which has been conducting an insurgency against the Turkish state since 1984.

The PKK is blacklisted as a terror group by Ankara and its Western allies.

The incident comes after Turkish President Recep Tayyip Erdogan threatened on Wednesday to launch an operation against the YPG in northern Syria, east of the Euphrates River, in the "next few days" and thus risking renewed tensions with the United States.

Washington has been working closely with YPG under the Kurdish-led Syrian Democratic Forces (SDF) alliance against the Islamic State (IS) extremist group.

Ankara has repeatedly condemned the United States for its military support to the YPG and it has been one of the biggest sources of tensions between the NATO allies.

Any new offensive by Turkey would be its third operation in Syria after previous operations against IS and the YPG in August 2016 and January 2018 respectively.

But Pentagon spokesman Commander Sean Robertson on Wednesday said any unilateral military action in Syria would be a "grave concern" and "unacceptable".

Erdogan's threats came hot on the heels of Washington's announcement of observation posts in Syria intended to prevent any altercation between the Turkish army and the YPG.

Later on Thursday, the Turkish defence ministry said air strikes struck PKK targets in Sinjar and Mount Karacak in northern Iraq, hitting shelters and tunnels.

Erdogan earlier this year threatened to expand Turkey's fight against the PKK to Iraq and launch an operation against the group in Sinjar, an area where the PKK has a presence.

The ministry said in a statement that the aim of the operation was "to prevent terror attacks against our citizens and security forces, and ensure border security."