Updated

Insurgents fired two shells at the Russian embassy in the Syrian capital on Tuesday as hundreds of pro-government supporters gathered outside the compound to thank Moscow for its intervention in Syria.

An Associated Press reporter was outside the embassy when the first shell slammed into the compound in central Damascus and smoke billowed from inside. As people started running away, another shell hit the area. No one was harmed in the shelling.

Russian Foreign Minister Sergey Lavrov condemned the attack, saying "this is obviously a terrorist act intended to, probably, frighten supporters of the war against terror and to not allow them to prevail in the fight with extremism."

An official with the Syrian Arab Red Crescent said no one was hurt in the shelling. The official, who spoke on condition of anonymity because he was not authorized to speak to the media, said the second shell hit about 200 meters (yards) from the embassy compound.

Rebels in the capital's suburbs have targeted the embassy in the past, and it was not clear if Tuesday's attack targeted the rally.

Insurgents have vowed to fight Russian forces after Moscow began launching airstrikes in Syria late last month.  Russia has been one of Assad's strongest supporters since the start of the uprising in 2011. The civil war has killed more than 250,000 people and displaced half of Syria's population.

Before the shelling, the demonstrators had gathered outside the embassy carrying posters showing Assad and Russian President Vladimir Putin, and waved the two countries' flags.

Some held placards that read: "Thanks Russia" and "Syria and Russia are together to fight terrorism."

"President Putin's stances were absolutely positive for Syria," said 39-year-old civil servant Nizar Maqsoud.

"All the West stood against us. Only Russia backed us . we are all here to thank Russia and President Putin," said Osama Salal, an 18-year-old student.

Russia began launching airstrikes in Syria on Sept. 30, allowing Syrian government forces to launch a multi-pronged ground assault. Moscow insists it is mainly targeting the Islamic State group and other "terrorists," but the ground-and-air offensive is being waged in areas controlled by U.S.-backed rebels as well as other insurgents, including the al-Qaida-affiliated Nusra Front.

The Syrian ground offensive continued for a seventh day Tuesday in central and northwestern regions, killing dozens of insurgents, according to Syrian state media.

SANA said troops captured the village of Lahaya hours after capturing the village of Mansoura on the northern edge of the central Hama province.

Lebanon's pro-Syrian daily Al-Akhbar and the Britain-based Syrian Observatory for Human Rights said civilian flights have stopped at the Basel Assad International Airport in the coastal province of Latakia because of intense activities by Russian warplanes at a nearby military base.

The airport, also known by its old name Hemeimeem, is being used by Iranian planes to bring in thousands of Iranian fighters to take part in the government offensive, said the Observatory, which relies on local activists.

Iran, another key ally of Assad, has sent military advisers to aid his forces but denies sending combat troops to Syria.

A civil aviation official in Damascus told The Associated Press that only international flights to the airport have been stopped, adding that internal flights continue as usual. He spoke on condition of anonymity because of the sensitivity of the topic.

Earlier Tuesday, the Nusra Front released an audio message purportedly from its leader, describing the Russian military intervention as a new "Crusader campaign" aiming to save Assad's rule.

The Nusra Front leader, known as Abu Muhammed al-Golani, called on Syrian militant and rebel groups to unite and intensify shelling of villages inhabited by members of Assad's minority Alawite sect.

Al-Golani also called on Muslims in the former Soviet Union to attack Russian civilians if Russians target civilians in Syria.

"The Russian intervention came to declare a new eastern Crusader war after the western Crusader war failed in Syria," al-Golani said, in an apparent reference to airstrikes by the U.S.-led coalition that began last year. Al-Golani said the Russians are not targeting the IS group, but are instead striking at militants who are fighting the government.

The jihadi leader promised to pay 3 million euros ($3.42 million) to whomever kills Assad and 2 million euros ($2.28 million) to whomever kills Hezbollah leader Sheikh Hassan Nasrallah, whose men are fighting alongside Assad's forces.