DAMASCUS, Syria — Russian warships in the Caspian Sea fired cruise missiles Wednesday 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 930 miles over Iran and Iraq and struck Raqqa and Aleppo provinces in the north and Idlib province in the northwest, Russian officials said. The Islamic State group has strongholds in Raqqa and Aleppo, while the al-Qaida-linked Nusra Front has a strong presence in Idlib.

U.S. Defense Secretary Ash Carter said Russia was continuing to strike targets other than Islamic State 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 its airstrikes in Syria, its longtime ally, on Sept. 30, and added a new dimension to the complex war that has torn the Mideast country apart since 2011.

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 President Bashar 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 string of setbacks in northwestern Syria in recent months.

The Islamic State group is not present in the areas where the ground fighting is underway.

The offensive in central Syria and the ensuing clashes with militants, including al-Qaida’s Syrian branch known as the Nusra Front, was the first major ground fighting since the Russian campaign began.

In televised remarks to President Vladimir Putin, Russian Defense Minister Sergei Shoigu said 26 missile strikes were carried out from four warships in the Caspian. Shoigu insisted the operation destroyed all the targets and did not launch any strikes upon civilian areas.

Andrei Kartapolov of the Russian General Staff told Russian news agencies that Russia had planned the missile strikes from the warships so that they would fly “over unpopulated areas.” Shoigu also said Russia has carried out 112 airstrikes on IS positions since Sept. 30.

Activists and rebels say the targets have included Western-backed fighters and other groups opposed to Assad’s government.

The Britain-based Syrian Observatory for Human Rights said a government offensive began on four fronts early Wednesday in Idlib and neighboring Hama provinces in what the group’s director Rami Abdurrahman described as “the most intense fighting in months.”

In Syria, the leader of a U.S.-backed rebel group, Tajammu Alezzah confirmed the ground offensive in a text message to The Associated Press, saying Russian and Iranian soldiers were involved in the operation. Russian officials deny sending any ground troops to the battlefield.

Maj. Jamil al-Saleh said the offensive, accompanied by air cover and shelling, came from three fronts, including Latamneh, north of Hama province where his group is based, and Kfar Zeita to the north. The offensive targeted the rural areas of Hama and Idlib that are almost totally controlled by rebel groups, he said.

Activist Ahmad al-Ahmad, who is in Idlib, said government troops “heavily” shelled central areas after rebels attacked an army post and destroyed a tank. He said the government advance covered an area of over 10 miles, and was a coordinated multipronged attack, the boldest push in the area by the government in months. The rebels repulsed back government troops, al-Ahmad said.

The Observatory, which has a network of activists in Syria, said the main launching point for government forces was the town of Morek on a highway that links Damascus with Aleppo, Syria’s largest city and its former commercial center. Rebels have controlled areas on the highway since 2012.

The Local Coordination Committees, another activist group, said rebels were able to destroy two tanks and an armored personnel carrier in northern parts of Hama province near Idlib. Video on social media by rebel fighters showed government tanks burning, apparently after being hit by U.S.-made TOW missiles.

The Observatory said 37 Russian air raids hit on Wednesday alone.

Two helicopters were seen flying low in Morek, but escaped militant fire, the Observatory said. It was not immediately clear if the pilots were Russians or Syrians, and Assad’s air force has Russian-made helicopters.

Although the Islamic State has no presence in the areas hit by airstrikes Wednesday, the Nusra Front is active in central and northern parts of the country — as are the Western-backed rebels. Russian officials have said the Nusra Front is among the groups it is targeting.

At a news conference in Rome, Carter said the U.S.-led coalition that also is conducting airstrikes in Syria has not agreed to cooperate with Russia in the fight against the Islamic State, and no collaboration is possible as long as Moscow continues to strike other targets.

He said the U.S. will conduct basic, technical talks with Russia about efforts to ensure that flights over Syria are conducted safely, and, “That’s it.”

Washington is not prepared to cooperate with a strategy of Russia’s that is “tragically flawed,” he said.

“They continue to hit targets that are not ISIL,” Carter said, using an acronym for the Islamic State group. “We believe that is a fundamental mistake.”

Since September 2014, the coalition has been hitting Islamic State positions mostly in northern and eastern parts of Syria, as well as in Iraq.

In Turkey, Prime Minister Ahmet Davutoglu renewed criticism of Russia’s airstrikes, insisting they were mainly targeting the moderate Syrian opposition and therefore helping strengthen IS.

He called on Moscow to respect Turkey’s airspace, saying the country would not “make any concessions” on matters concerning its border security.

Russian warplanes violated Turkey’s borders on two separate occasions over the weekend, drawing strong protests from Turkey’s NATO allies. Turkey scrambled F-16s in response and also summoned the Russian ambassador to lodge protests.

Turkey’s Foreign Ministry said it had proposed a meeting between Turkish and Russian military officials in Ankara on avoiding Russian infringements of its airspace.

Syrian state TV quoted an unidentified Syrian military official as saying that Russian warplanes attacked Islamic State group positions in the towns of Al-Bab and Deir Hafer in Aleppo province.

Russia’s entry into the crowded and sometimes uncoordinated air wars in Syria is making the U.S. increasingly nervous, reflecting concern at the Pentagon and in Europe about the risk of accidents or unintended conflict.

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Vasilyeva reported from Moscow. Associated Press writer Suzan Fraser in Ankara, Turkey and Sarah El Deeb and Bassem Mroue in Beirut contributed to this report.