Russian military forces fired rockets and launched artillery at Syrian rebels, some backed by the U.S., in a dramatic recent escalation of tensions, a senior military official tells Fox News.
The rockets come from the BM-30 SMERCH multiple rocket launch system, the official says, adding that they were moved two days ago from an airbase in Latakia, a coastal stronghold for the Assad regime.
Syria's top general on Thursday said Russian strikes had helped government forces launch a "wide-ranging" offensive in central and northwestern Syria, where al-Qaida's affiliate as well as other insurgents had advanced toward key government strongholds in recent months.
Gen. Ali Ayoub, the Syrian chief of staff, said in a rare televised statement that the Russian strikes have facilitated an expanded military operation to eliminate "terrorists" -- a term the Syrian government uses to refer to all armed opposition to the Syrian government.
The Syrian ground push got a boost after Russian warships launched cruise missiles into Syria from the Caspian Sea on Wednesday, bringing new military might into the nearly five-year civil war. The strikes have alarmed the U.S. and its NATO allies, particularly Turkey, and the alliance's defense ministers were to meet later Thursday.
Russian officials say the 26 cruise missiles 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-Qaida affiliate, the Nusra Front, has a strong presence in Idlib. Activists in Raqqa said at least one of the missiles landed in an open area in the nearby town of Tabqa, causing a huge explosion.
Russia says its intervention is aimed at helping the Syrian government defeat the Islamic State group, but local activists and U.S. officials say the strikes have also targeted Western-backed rebels.
The Britain-based Syrian Observatory for Human Rights said Russian airstrikes in Idlib killed at least seven civilians on Wednesday. At least 40 civilians were killed on the first day of the Russian airstrikes last week, according to activists and a human rights group.
"After the Russian airstrikes, which reduced the fighting ability of Daesh and other terrorist groups, the Arab Syrian armed forces kept the military initiative," Ayoub said, using the Arabic acronym for ISIS.
"Today, the Syrian Arab armed forces began a wide-ranging attack with the aim of eliminating the terrorist groups and liberating the areas and towns that suffered from their scourge and crimes."
The heavy fighting was concentrated in the rural areas of Idlib, Hama and Latakia provinces, where the Army of Conquest, a coalition of rebel groups that includes the Nusra Front, operates. The Western-backed Free Syrian Army also has a presence in the area. ISIS has a limited presence in western Hama, away from where the clashes erupted.
Syrian TV showed footage of Syrian soldiers loading and firing artillery, as helicopters flew over rural Hama and Idlib. It also showed tanks and airstrikes.
The Observatory and other activists said a military helicopter was downed in Kfar Nabouda, in northern Hama. A local media group said the helicopter belonged to the Syrian government. The Observatory said Russian jets bombed areas near Kfar Nabouda.
The head of the Observatory, Rami Abdurrahman, said the troops moved from the village of Jorin in rural Latakia into Sahl al-Ghab, a vital plain that lies between Latakia, Hama and Idlib. The Observatory relies on a network of activists across the war-torn country.
Government troops appear intent on driving rebels from the area, adjacent to the heartland of Assad's family and the Alawite minority -- an offshoot of Shiite Islam -- to which it belongs. Foreign fighters, particularly from Asia and China's ethnic Uighur minority, have a strong presence in the area, according to Abdurrahman.
Lebanon's Al-Manar TV, which belongs to the Shiite militant group Hezbollah, a key ally of Assad's forces, said the Syrian army seized control of al-Bahsa village in Hama on Thursday.
Syria State news agency SANA said joint Syrian-Russian airstrikes hit 27 targets belonging to Nusra Front, including positions and training camps in rural Latakia.
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.
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 opposition groups.
Turkish President Recep Tayyip Erdogan warned that Moscow's military action in Syria is endangering trade ties with his country. Speaking to journalists while en route from Brussels to Tokyo, Erdogan warned that 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.
In Russia, Vladimir Putin's spokesman said the president had been informed about Erdogan's remarks but hoped they would not affect relations between the two countries.
"We sincerely hope that these relations will continue to expand according to the plans mapped out by Putin and Erdogan because this cooperation is genuinely mutually beneficial and is in the interests of both our countries," Dmitry Peskov told reporters on Thursday.
The Associated Press contributed to this report.