More than 100 Turks are being quarantined after returning from coronavirus-hit Iran, Turkey's health minister said on Tuesday.

The UN refugee agency on Thursday appealed to Turkey to take in more refugees from Syria, as hundreds of thousands flee the regime's brutal assault on the last rebel enclave.

Russian President Vladimir Putin and Turkish leader Recep Tayyip Erdogan have discussed de-escalation of the Syrian crisis, the Kremlin said Wednesday, adding that Russian-Turkish agreements should be implemented in full.

Turkey threatened on Saturday to respond if any of its military outposts in Syria's last opposition bastion of Idlib came under attack, a day after officials said three of them had been encircled by forces loyal to Damascus. 

Greece has sought to bolster its Mediterranean presence in recent weeks in response to heightened tension with Turkey, ramping up its meanoeuvres but sparking accusations of adventurism at home.

Turkey has sent nearly 150 vehicles with commandos and ammunition to reinforce its observation posts in Idlib, Syria's last rebel-held region, Turkish state news agency Anadolu reported Friday.

Flights resumed Thursday at an Istanbul airport after a Turkish airliner skidded off a runway, killing three people and injuring 180 others.

Sabiha Gokcen Airport restarted operations at around 4 a.m. (0100 GMT) though delays and cancellations continued.

Syrian militants affiliated with groups such as al-Qaida and the Islamic State group are currently being sent by Turkey to fight on behalf of the U.N.-supported government in Libya, according to two Libyan militia leaders and a Syrian war monitor.

Both sides in Libya's civil war receive equipment and backing from foreign countries. But Turkey, which has long trained and funded opposition fighters in Syria and relaxed its borders so foreign fighters joined IS, has in recent months been airlifting hundreds of them over to a new theater of war in Libya.

Turkey warned Russia not to get involved as it retaliated against Syrian government forces for killing four of its soldiers in northwest Syria on Monday.

A powerful earthquake has killed at least 21 people and injured more than 1,000 in eastern Turkey, as rescue teams searched through the rubble of collapsed buildings for survivors on Saturday.