Russian authorities have confirmed that an Airbus A320 came under threat while flying through Syrian airspace.
The aircraft, operated by Nordwind Airlines, was conducting a charter service from the Egyptian resort of Sharm el-Sheikh to the Russian city of Kazan on 29 April.
Russia's transport ministry, citing the federal aviation regulator Rosaviatsia, says the crew of the A320 noted evidence of "combat" which "threatened the safety of the aircraft".
The country's foreign ministry says there were 159 passengers on board the aircraft when the incident occurred, at 04:55 Moscow time.
While the airframe identity is unconfirmed, ground-based surveillance data indicates that, at this time, a Nordwind A320 registered VP-BJH and operating flight 1980 was passing over central Syria en route to Kazan.
It is unclear whether the threat came from surface-to-air missiles or a different source. The aircraft landed safely in Kazan, the transport ministry adds.
Russia's foreign ministry says it has taken "urgent measures" to clarify "all the circumstances" of the event, and is in contact with Syrian authorities.
Syrian airspace has been avoided by a number of carriers after assessments of the potential risk to flights.