UN secretary-general Antonio Guterres called for an immediate de-escalation in Syria after Israel carried out raids inside the country.
"The secretary-general is following closely the alarming military escalation throughout Syria and the dangerous spillover across its borders," UN spokesman Stephane Dujarric said in a statement.
"The latest events come as the Syrian people suffer through one of the most violent periods in nearly seven years of conflict.
"Over 1,000 civilian casualties from air strikes were reported in the first week of February alone."
Israel targeted what it said were Iranian positions inside Syria after one of its jets was hit by Syrian air defences and crashed. The pilots ejected and the plane crashed inside Israel. One crew member was severely wounded, but his condition was said to be improving on Sunday. The incident was Israel's first loss of a warplane in battle since 1982.
The Israeli raids came after it intercepted what it said was an Iranian drone entering its airspace from Syria. Israel has sought to stay out of direct involvement in the Syrian war, but it acknowledges carrying out dozens of air strikes there to stop what it describes as deliveries of advanced weapons to Lebanese Shiite group Hezbollah.
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Meanwhile Turkey announced on Sunday the death of another soldier in its operation against the Peoples' Protection Units (YPG) in Kurdish-controlled Afrin.
Sunday's announcement brings to 31 the number of Turkish soldiers killed since the operation against the YPG started on January 20 with Ankara's cross-border incursion into the enclave of Afrin.
Saturday was the deadliest single day for Turkey, with 11 Turkish soldiers killed. Two of them were aboard a Turkish attack helicopter that crashed while on a mission over Afrin. The YPG claimed they brought down the helicopter, but Turkish officials did not confirm that account.
Also Sunday, at least three civilians were killed in government airstrikes and shelling on a besieged, opposition-held area outside Damascus, according to the Observatory for Human Rights. The Syrian Civil Defense search-and-rescue group said two people had been killed in the Eastern Ghouta region.
Rebels fired shells from Eastern Ghouta into Damascus, striking popular squares in and around the old city, Syrian state media reported. There were no immediate reports of casualties.
Mr Guterres stressed that all concerned in Syria and in the region must abide by international law and the relevant Security Council resolutions.
"He calls on all to work for an immediate and unconditional de-escalation of violence and exercise restraint," Mr Dujarric said.
"The secretary-general further calls on the parties to move swiftly toward a political solution, in line with Security Council Resolution 2254, which is the only way to end the violence and the terrible suffering of the Syrian people."
The confrontation between Iran and Israel early Saturday was the most serious since Syria's war began in 2011. It also came amid growing alarm over Syrian government offensives against rebel-held Eastern Ghouta and Idlib.
Israel's ambassador Danny Danon called on the Security Council "to condemn this dangerous act and to put an immediate end to Iranian provocations".
Diplomats, however, said there were no immediate plans to convene a council meeting despite the sharp rise in tensions.
The council is due to discuss the crisis in Syria on Wednesday.
