Russia is to send new anti-aircraft missiles to Syria, a week after Syrian forces accidentally shot down a Russian aircraft during an Israeli air strike.
Russian Defence Minister Sergei Shoigu said that the S-300 surface-to-air missile defence system would be delivered within two weeks.
Fifteen Russian military personnel were killed when the reconnaissance aeroplane was downed on 17 September.
Syria and Russia say Israel was to blame, but it denies responsibility.
In remarks quoted by Russian news agency Interfax, Mr Shoigu said the delivery of the system had been suspended in 2013 following a request from Israel, but added: “Now, the situation has changed. And it’s not our fault.”
Russian plane downed in Syria: What may happen next?
Why is there a war in Syria?
“In parts of the Mediterranean adjacent to Syria, there will be radio-electronic jamming of satellite navigation, onboard radars and communications systems used by military aircraft attacking targets in Syrian territory,” he said.
The systems will also be able to track and identify Russian aircraft.
Russia is supporting President Bashar al-Assad in Syria’s civil war.
What happened last week?
The incident is reported to have occurred about 35km (22 miles) from the Syrian coast as the Ilyushin Il-20 aircraft was returning to Russia’s Hmeimim airbase near the north-western city of Latakia.
Russia’s Tass news agency said at the time that the plane “disappeared during an attack by four Israeli F-16 jets on Syrian facilities in Latakia province”.
Reports on Syrian state media spoke of an attack in the area shortly before the plane disappeared. According to Sana news agency, the military said it had intercepted “enemy missiles coming from the open sea towards the city of Latakia”.
Syrian television also reported explosions over the sky in Latakia just before 22:00 local time. Thirty minutes later, the Sana Facebook page reported that Syrian air defences had responded to enemy missiles.
What does Russia say?
On Sunday, Russia reiterated its stance that Israeli jets had used its reconnaissance plane as cover while carrying out strikes in Syria.
The country’s defence ministry said Israel had failed to give it adequate notice of the attack, putting the Russian aircraft in the path of Syrian air defence systems.
“The actions of the Israeli fighter pilots, which resulted in the loss of life of 15 Russian servicemen, either lacked professionalism or were an act of criminal negligence, to say the least,” a ministry spokesman said.
How has Israel responded?
Israel maintains that indiscriminate fire from Syrian forces was to blame for the incident.
It said its aircraft were targeting Syrian military facilities “from which systems to manufacture accurate and lethal weapons were about to be transferred on behalf of Iran to Hezbollah in Lebanon”.
The Lebanese Shia militant group and Iran are both allies of the Syrian government. Israel has reportedly hit more than 200 Iranian targets in Syria over the past 18 months.
In a statement on Sunday evening, the Israel Defense Forces said that figures in the Russian military had been clear “that the deconfliction mechanism worked and did so in a timely manner”.
Is Russia taking over Syria’s air defences?
Analysis by Jonathan Marcus, BBC Defence Correspondent
In striking at targets close to the Russian air base near Latakia, the Israeli Air Force appears to have crossed a Russian red line. Furthermore the loss of its aircraft has compelled Moscow to act. But its intentions remain unclear.
Israel insists that interrupting weapons supplies to Hezbollah and constraining Iran’s growing influence in Syria are vital strategic goals.
But Russia seems to be saying it is no longer willing to turn a blind eye to such operations, which it believes are weakening the Syrian leader President Assad.
If this really is Moscow’s intention then the Israelis are going to have to tread carefully. There could be some very tense and bumpy moments in the coming weeks and months.