A Russian reconnaissance plane has been shot down by a Syrian missile over the Mediterranean Sea, killing all 15 people on board, according to the Russian Defence Ministry — and Moscow is blaming Israel for the crash.

Key points: Russia says the plane was caught in the crossfire as Israeli fighters attacked Syrian targets

Russia says the plane was caught in the crossfire as Israeli fighters attacked Syrian targets Russia says the Israeli fighters were using the Russian plane as a shield

Russia says the Israeli fighters were using the Russian plane as a shield Israel says the plane fell victim to the "extensive and inaccurate" firing of Syrian surface-to-air missile systems

The Russian military said the aircraft was caught in the crossfire on Monday as four Israeli fighter jets attacked targets in north-western Syria.

It said the Il-20 reconnaissance plane was hit while 35 kilometres offshore and returning to its home base nearby.

"The Israeli pilots were using the Russian aircraft as a shield and pushed it into the line of fire of the Syrian defence," Defence Ministry spokesman Major General Igor Konashenkov said.

Russian Defence Minister Sergei Shoigu called his Israeli counterpart, Avigdor Lieberman, later on Tuesday to say Israel was "fully to blame" for the deaths, the ministry said.

For several years, Israel and Russia have maintained a special hotline to prevent their air forces from clashing in the skies over Syria, and Israeli military officials have previously praised its effectiveness.

But the Russian military said Israel did not warn it of its operation over Latakia province until one minute before the strike, which did not give the Russian plane enough time to escape.

Sorry, this video has expired Donald Trump says Syria is responsible for Russian plane shooting

Israel has offered its condolences over the death of the Russian troops but said it holds the Syrian Government "fully responsible".

The Israeli military said the Russian plane fell victim to the "extensive and inaccurate" firing of Syrian surface-to-air missile systems and that the Israeli jets — which were carrying out a raid against a Syrian Government facility in another place — had already left Syrian airspace, and were back within Israeli airspace, when the incident occurred.

Israel also blamed Iran and Hezbollah for what it described as the "unfortunate incident".

The Russian Defence Ministry said a recovery operation had already located the plane's wreckage at sea and had retrieved some bodies and some fragments of the plane.

DMZ to be set up in Idlib, delaying offensive

Fighters from several rebel groups would have to adhere to the plan if it were to succeed. ( AP: Ugur Can/DHA )

Meanwhile, the leaders of Russia and Turkey have agreed to establish a demilitarised zone in Syria's Idlib region, the last major stronghold of anti-government rebels, where fears have been running high of a devastating offensive by government forces.

The zone will be established by October 15 and be 15 to 20 kilometres deep, with troops from Russia and NATO member Turkey conducting coordinated patrols, President Vladimir Putin said after meeting with Turkish President Recep Tayyip Erdogan in Sochi.

The deal marked a significant agreement between the two leaders and effectively delays an offensive by Syria and its Russian and Iranian allies, one that Turkey fears would create a humanitarian crisis near its border.

Mr Putin said "radical militants" such as the Al Qaeda-linked Hayat Tahrir al-Sham would have to withdraw from the zone.

The group denies it is linked to Al Qaeda.

Asked whether Syrian President Bashar al-Assad's government agreed with the plan, Russian Defence Minister Sergei Shoigu told reporters in Sochi that "in the coming hours, we will agree with them on all the positions put forth in this document".

In recent weeks, Russian officials have repeatedly said that rebels in Idlib were preparing a chemical weapons attack that could be blamed on the Syrian Government and prompt a retaliatory strike by the West.

Turkey had appealed to Russia and Iran, its uneasy negotiating partners, for a diplomatic resolution. At the same time, it has sent reinforcements to its troops ringing Idlib, a move designed to ward off a ground assault, at least for now.

Reuters/AP