Moscow said Israeli airstrikes on Monday evening directly led to the downing of a Russian reconnaissance aircraft by Syrian regime air defences over the Mediterranean Sea, and threatened a "response" to the incident.
Russian Defence Minister Sergei Shoigu spoke to his Israeli counterpart Avigdor Lieberman, and told him Moscow holds Israel wholly to blame for the shooting down of a Russian military plane near Syria, according to Reuters.
"The full blame for the shot-down Russian plane and death of the crew is on the Israeli side," Shoigu told Lieberman in a phone call, according to a ministry statement, adding that Russia "reserves the right to future response measures".
It said the plane was caught in the crossfire as four Israeli fighters attacked regime targets in Latakia province, in northwestern Syria, with all 15 crew missing.
The Russian military said the Il-20 reconnaissance aircraft was hit 35 kilometres (22 miles) off the coast of Syria as it was returning to its home base in Latakia province.
"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 Maj. Gen. Igor Konashenkov said in a statement.
Russia said it would make an "appropriate response" to Israel.
"As a result of the irresponsible actions of the Israeli military, 15 Russian service personnel perished. This absolutely does not correspond to the spirit of Russian-Israeli partnership," Interfax news agency quoted Russian defence ministry spokesman Igor Konashenkov as saying.
"We reserve the right to take commensurate measures in response," Konashenkov was quoted as saying.
Konashenkov described the Israeli military's actions as hostile and an act of provocation, the agency added.
Russia 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.
A recovery operation in the Mediterranean Sea is underway, Konashenkov said.
For several years, Israel and Russia have maintained a special hotline to prevent their air forces from clashing in the skies over Syria. Military officials have previously praised its effectiveness, with no crossed wires despite scores of Israeli strikes in Syria.
Russia has been a key backer of Syrian President Bashar al-Assad and it has two military bases in the country, including one close to the Mediterranean coast.
The Israeli military said earlier on Tuesday that it had no reaction, saying it does not comment on "foreign reports".