LONDON: At least 33 Turkish soldiers were killed after Syrian government forces fired airstrikes in Idlib on Thursday, the Syrian Observatory for Human Rights said.

The airstrike took place in an area between the towns Baluon and Al-Bara in Idlib, and was a response to Turkey-backed opposition forces recapturing the strategic town of Saraqeb earlier on Thursday.

Turkey retaliated with strikes against the regime, the presidency announced early Friday.

"Known targets of the regime have come and will continue to come under fire from the air and ground," Turkish President Recep Tayyip Erdogan's communications director, Fahrettin Altun, said in a statement.

"We urge the international community to fulfil its responsibilities," Altun added.

Turkish President Tayyip Erdogan chaired an emergency security meeting late on Thursday to evaluate the latest developments in the northwestern Syrian province of Idlib, two Turkish security sources said.

The local governor of the southeastern Turkish province of Hatay announced the death toll early Friday.

Rahmi Dogan said none of the remaining wounded soldiers were in critical condition.

Russia's Defence Ministry said the Turkish troops hit by shelling should not have been in the Syrian area where they were and that Ankara had not informed Moscow in advance about their location, the RIA news agency reported.

The ministry said, however, that Russian war planes had not carried out strikes in the area where Turkish troops were and that Russia had done everything to ensure the Syrian army ceased fire to allow the troops to evacuate.

Russia is sending two warships equipped with Kalibr cruise missiles to the Mediterranean Sea towards the Syrian coast, the Interfax news agency cited Russia's Black Sea Fleet as saying on Friday.

The United States on Thursday demanded that the Syrian regime and its ally Russia end their "despicable" operation in Idlib province

"We stand by our NATO ally Turkey and continue to call for an immediate end to this despicable offensive by the Assad regime, Russia and Iranian-backed forces," a State Department spokesperson said.

"We are looking at options on how we can best support Turkey in this crisis."

Major social media platforms and messaging apps appeared to be blocked across Turkey on Thursday evening, said NetBlocks, a civil society group which monitors digital services globally.

The group said: “Social platforms Twitter, Facebook and Instagram became unreachable at 11:30 p.m. local time (8:30 p.m. UTC) via national provider Turk Telecom (AS9121) and subsequently other leading service providers. Data show that YouTube and WhatsApp messaging backend servers were also partially restricted at the same time or shortly after. The restrictions are technically consistent with techniques used to filter content in Turkey,” in a report Thursday.

The United Nations on Thursday called for urgent action in northwest Syria, warning that "the risk of greater escalation grows by the hour."

"The Secretary-General reiterates his call for an immediate ceasefire and expresses particular concern about the risk to civilians from escalating military actions," spokesman Stephane Dujarric said in a statement.

"Without urgent action, the risk of even greater escalation grows by the hour."

The Syrian Observatory for Human Rights also reported on Thursday that Russian-backed government forces had seized full control of southern Idlib province after fresh advances against the rebels.

Government forces have seized about 60 towns and villages in the southern Idlib area and the adjoining province of Hama in the last three days, the Observatory said.