DEVELOPING: Four cruise missiles launched from a Russian warship aimed at targets in Syria missed their target and crashed in Iran Thursday, a senior defense official told Fox News.

The “Kalibr” cruise missiles were fired for the first time in combat from warships in the Caspian Sea, the official said.

There was no immediate word of any damage or casualties in Iran.

Russia began launching missiles into Syria from warships on Wednesday, The Associated Press reported.

Russian officials said 26 cruise missiles launched from warships have already hit the provinces of Raqqa and Aleppo in the north and Idlib province in the northwest. The Islamic State group has strongholds in Raqqa and Aleppo, while Syria's Al Qaeda affiliate, the Nusra Front, has a strong presence in Idlib.

More On This...

Russia says its military intervention is aimed at helping the Syrian government defeat ISIS, but local activists and U.S. officials say the strikes have also targeted Western-backed rebels.

Syria's conflict, which began as an uprising against Assad in March 2011 but descended into a full-blown civil war after a fierce government crackdown, has so far killed 250,000 people, according to U.N. figures.

The Russian intervention is supported by an intelligence sharing center set up in Baghdad to coordinate the efforts of Russia, Iraq, Iran and Syria.

Russia's intervention has strained ties with NATO, particularly Turkey, which shares a long border with Syria and has been a leading backer of the Syrian rebels. Turkey and its allies say the Russian strikes have mainly targeted moderate Syrian rebels.

Turkish President Recep Tayyip Erdogan warned that Moscow's military action in Syria is endangering trade ties with his country, saying Ankara could look elsewhere for gas supplies and cancel the construction of its first nuclear power plant, which is being built by Russia. Russia supplies 60 percent of Turkey's gas needs.

"Losing Turkey would be a serious loss for Russia," Erdogan said, in comments published Thursday in the Hurriyet newspaper.

Over the weekend, Turkey reported back-to-back violations of its airspace by Russian warplanes. Russia called its penetration of Turkish airspace a minor incident that was unintentional.

Fox News’ Lucas Tomlinson and The Associated Press contributed to this report.