Frame grab shows shows Russian warships sailing in the Caspian Sea.

Russian warships in the Caspian Sea fired cruise missiles on Wednesday night as Syrian government troops launched a ground offensive in central Syria in the first major combined air-and-ground assault since Moscow began its military campaign in the country last week.

The missiles flew nearly 1,500km over Iran and Iraq and struck Raqqa and Aleppo provinces in the north and Idlib province in the northwest, Russian officials said. ISIS has strongholds in Raqqa and Aleppo, while the al-Qaeda-linked Nusra Front has a strong presence in Idlib.

U.S. Defense Secretary Ash Carter said Russia was continuing to strike targets other than ISIS militants, adding that he was concerned about the Syrian ground offensive backed by Moscow’s airpower.

The latest developments came a week after Russia began airstrikes in Syria, its longtime ally, on Sept. 30, and added a new dimension to the complex war that has torn apart the country since 2011.

Activists and rebels say the targets have included Western-backed fighters and other groups opposed to President Bashar Assad.

A Syrian official and activists said government troops pushed into areas in the central province of Hama and south of Idlib in the boldest multipronged attack on rebel-held areas, benefiting from the Russian air cover. The official spoke on condition of anonymity because he was not authorized to talk to the media.

Moscow has mainly targeted central and northwestern Syria, strategic regions that are the gateway to Assad’s strongholds in Damascus, and along the Mediterranean coast where Russia has a naval base.

The Russian airstrikes strikes appear to have emboldened Syrian troops to launch the ground push after a series of setbacks in northwestern Syria in recent months.

ISIS is not present in the areas where the ground fighting is underway. However, The Russian defence ministry said on Wednesday that 26 rockets fired by its warships earlier in the day had struck targets associated with ISIS and Nusra Front, the Interfax news agency reported.