A Russian Military Aircraft carrying 14 service members disappeared off the Syrian coast on Monday as Israeli fighter jets were attacking targets in the area and a French ship was launching missiles, Russian news agencies reported, citing the Russian Defense Ministry.

The Defense Ministry said that the Il-20 surveillance plane disappeared from radar screens Monday night when it was 22 miles from the Mediterranean coast. The aircraft had been returning to a Russian air base near the Syrian port city of Latakia, and the Defense Ministry said it had organized a search-and-rescue operation.

“The Il-20 disappeared from air traffic control radars during an attack by four Israeli F-16 planes on Syrian facilities in the Latakia governorate,” the Defense Ministry said, according to the news agency Interfax. “At the same time, Russian air traffic control radars recorded launches of missiles from the French frigate Auvergne that was in this area.”

The Israeli military did not respond to inquiries about the missing plane, The Associated Press reported, saying it does not comment on “foreign reports.” Col. Patrik Steiger, a spokesman for the French military, told Reuters, “We deny any involvement.”

The disappearance came the same day that the Russian defense minister, Sergei K. Shoigu, said that Syria would refrain from launching an offensive on Idlib Province, the last major rebel stronghold in Syria.

Russia has been the most important backer for President Bashar al-Assad of Syria during the country’s long-running civil war, now approaching eight years, and it has sent warplanes and troops to support him, recently deploying a large flotilla of warships to the region.

Mr. Shoigu’s announcement came after President Vladimir V. Putin of Russia and his Turkish counterpart, Recep Tayyip Erdogan, appeared to delay what had been forecast to be a bloody assault on Idlib by agreeing to establish a “demilitarized zone” there.

At least three million Syrian civilians and 30,000 insurgent fighters, including Qaeda-linked jihadists, have been cornered in Idlib, the last significant piece of territory in Syria that Mr. Assad does not control.

Capt. Bill Urban, a spokesman for the United States Central Command, referred questions on the episode to the Russian Defense Ministry. “The U.S. was not involved in any strikes in Western Syria or in the shoot down of any planes tonight,” he said on Monday evening.