A Russian military transport plane has crashed in Syria killing more than 30 people, the defence ministry says.
The An-26 plane crashed during landing at Hmeimim airbase, near the coastal city of Latakia, the ministry is quoted as saying by Russian media.
It says all 39 military personnel on board died, not 32 as earlier reported.
The plane was not fired upon, the ministry says, and preliminary data suggests a technical malfunction could have caused the crash.
An investigation is now under way. Russian President Vladimir Putin expressed condolences to the victims' relatives.
Meanwhile, medics in the rebel-held Eastern Ghouta area of Syria say they have been treating people with breathing problems after a suspected chlorine attack.
The reports follow government air strikes and shelling just hours after the last UN aid envoy left the enclave following a supposed five-hour truce.
In a separate development, UN war crimes investigators say air strikes in Syria by both Russia and the US-led coalition killed large numbers of civilians last year.
What is known about Tuesday's plane crash?
The Russian defence ministry says the An-26 crashed at about 15:00 Moscow Time (12:00 GMT).
It says the plane went down about 500m (1640ft) from the runway.
A special commission is to be set up to investigate the crash.
This was just a week after Russian warplanes were damaged at the airbase in a rebel mortar attack.
Hmeimim is Russia's main base for air strikes on rebel groups in Syria - strikes that have enabled Syrian President Bashar al-Assad's forces to recover much lost ground.
What are Russia's air force losses in Syria?
Russia launched its military operation in September 2015, saying it was acting upon a request by President Assad.
Here are the confirmed air force losses:
- Feb 2018: A Sukhoi-25 warplane is shot down in a rebel-held area in north-western province of Idlib. The pilots ejects but later dies in a ground fight
- Dec 2017: Shelling damages several planes at the Hmeimim airbase, with two Russian servicemen killed
- Dec 2016: A Tu-154 carrying 92 people - including army musicians - crashes into the Black Sea after taking off for Syria from Sochi, killing all on board
- Aug 2016: All five people on board a helicopter are killed when it is shot down over Idlib
- Nov 2015: Turkish warplanes shoot down a Sukhoi-24. One pilot is killed, the other rescued. The incident sparks a severe deterioration of bilateral relations
What about the suspected chlorine attack in Eastern Ghouta?
The attack targeted the town of Hammoria and led to the evacuation of dozens of civilians, according to the Syrian Civil Defence, whose volunteer rescue workers are widely known as the White Helmets.
Local medics said they were treating a number of people who had breathing problems.
Syria denied allegations it had carried out the attack, dismissing them as an act of desperation by Western powers.
Meanwhile, Russia - a key ally of the Syrian government - offered rebels safe passage out of the area.
What did UN war crimes investigators say?
They said they found that an attack by the US-coalition on a school near the city of Raqqa last March killed 150 local residents - many times more than Washington had admitted to.
The investigators also said Russian air strikes on a market in Atareb, west of Aleppo, killed at least 84 people last November.
Their report talked too of chemical weapons attacks by Syrian government forces, and war crimes allegedly committed by their rebel opponents.