DAMASCUS, Syria — Backed by Russian airstrikes, Syrian government forces on Thursday pushed into the ancient town of Palmyra that has been held by the Islamic State group since May, state TV reported, as an Iraqi military spokesman announced the start of a long-awaited military operation to recapture the northern city of Mosul from IS militants.

The advance on Palmyra, a UNESCO world heritage site, came after the troops managed this week to capture several hills and high ground around the town, famed for its priceless archaeological site and Roman ruins. Syrian troops have been on the offensive for days in an attempt to capture the town.

The fall of Palmyra to IS militants last year had raised concerns world over, and the destruction the extremists subsequently embarked upon sent shock waves through archaeological circles and beyond. It was also a big blow to the government of Syrian President Bashar Assad whose forces pulled out with apparently little fighting.

On Thursday, Syrian state TV broadcast footage of its reporter, embedded with the Syrian military, speaking live from the entrance of Palmyra and saying that as of midday, the fighting was concentrated near the archaeological site on the southwestern edge of the town.

Cracks of gunfire and explosions echoed as the reporter spoke. The TV also aired footage showing soldiers walking and SUVs driving near a building that appears to have been a hotel.

An unnamed Syrian soldier told the station he had one message for the Islamic State group: “You will be crushed under the feet of the Syrian Arab Army.”

Recapturing the town would be a significant victory for Syria’s army and its Russian allies. Russia withdrew most of its forces and aircraft from Syria last week after a months-long bombing campaign that succeeded in turning the tide of the war again in President Bashar Assad’s favor.

However, Turkey-based activist Osama al-Khatib, who is originally from Palmyra, denied that Syrian troops had entered the town. He said they were still on the edge of Palmyra and that the video seen on Syrian state TV shows the area about 5 kilometers (3 miles) from Palmyra.

Earlier in the day, Gov. Talal Barazi told The Associated Press from the nearby city of Homs that the Syrian army has determined three directions to storm Palmyra and was clearing all roads leading into the town of mines and explosives.

“We might witness in the next 48 hours an overwhelming victory in Palmyra,” Barazi said over the phone, adding that “the army is advancing in a precise and organized way to protect what is possible of monuments and archaeological sites.”

The Britain-based Syrian Observatory for Human Rights said Syrian troops and Shiite militiamen helping them on the ground were facing tough resistance from IS extremists as they try to penetrate the town’s limits.

The Observatory, which monitors the Syrian conflict through a network of activists on the ground, said the IS lost over 200 militants since the government campaign to retake Palmyra began 17 days ago. It did not have figures for government losses.

Before the outbreak of Syria’s civil war, which just entered its sixth year, Palmyra had attracted tens of thousands of tourists to Syria every year. It is affectionately known by Syrians as the “bride of the desert.”

In Palmyra, the IS destroyed many of the town’s Roman-era relics, including the 2,000-year-old Temple of Bel and the iconic Arch of Triumph, and also killed dozens of captive Syrian soldiers and dissidents from IS in public slayings at the town’s grand roman theater and other ruins.

Along with blowing up priceless archaeological treasures, among the first destructions IS carried out in Palmyra was the demolishing of the town’s infamous Tadmur prison, where thousands of Syrian government opponents had been imprisoned and tortured over the years.

Also Thursday, an Iraqi military spokesman announced in Baghdad that the army, backed by U.S.-led coalition aircraft, has launched an operation to recapture Mosul, Iraq’s second-largest city, from IS militants.

In the push, Iraqi forces retook several villages on the outskirts of the town of Makhmour, east of Mosul, early in the morning on Thursday and hoisted the Iraqi flag there, according to the spokesman for the Joint Military Command, Brig. Gen. Yahya Rasool.

But taking Mosul is no small goal and it was not immediately clear how long such a complex and taxing offensive would take. Only recently, Iraqi and U.S. officials refrained to give a specific time on when the Mosul operation could begin, saying it would take many months to prepare Iraq’s still struggling military for the long-anticipated task of retaking the key city.

Iraqi state-run TV interrupted its morning program with a series of news alerts announcing the operation and broadcasting patriotic songs and flag-waving video clips.

Rasool told The Associated Press that the U.S.-led international coalition was providing air support but would not divulge more details on the offensive, which he said was dubbed “Operation Conquest.”

Mosul fell to the Islamic State group during the militants’ June 2014 onslaught that captured large swaths of northern and western Iraq and also neighboring Syria.

The advance on Palmyra comes against the backdrop of Syrian peace talks underway in Geneva between representative of the Damascus government and the Western-backed opposition. The talks, which have been boosted by a Russia-U.S.-brokered cease-fire that has mostly held since late February, were to adjourn on Thursday — without having achieved any apparent breakthroughs.

The negotiations are scheduled to resume later in April.

In Moscow, U.S. Secretary of State John Kerry called on Thursday for countries to boost efforts to fight IS in Syria, Iraq and beyond in the wake of this week’s deadly attacks in Brussels. He said the Brussels attack should put nations on notice that the terror threat emanating from the Middle East must be stopped.

Kerry is in Moscow for talks with Russian President Vladimir Putin and Foreign Minister Sergey Lavrov on Syria, Ukraine and the Brussels attacks.