BEIRUT — Backed by Russian aircraft, Syrian troops pushed Friday toward the historic central town of Palmyra in an offensive to recapture it from the Islamic State group whose fighters have damaged some of the world’s most precious archaeological sites since they overran the town last May.

After night fell, Syria’s state news agency SANA reported that the offensive advanced toward Palmyra and that scores of IS fighters have been killed or wounded in Syrian artillery fire near the town. The reports gave no casualty numbers or other details.

Activists who monitor the Syrian conflict reported intense airstrikes in Palmyra and its suburbs. In Moscow, a Russian Defense Ministry official confirmed his country’s warplanes in Syria were flying in support of the Syrian offensive.

Lt. Gen. Sergei Rudskoi said Russian aircraft were conducting 20-25 sorties a day in support of the Palmyra offensive, even though Russia this week drew down its military presence in Syria after President Vladimir Putin ordered a partial pullout of Russian aircraft and forces from Syria, in support of the Geneva peace talks.

The U.N.-brokered talks between representatives of the Syrian government and the Western-backed opposition adjourned for the weekend after five days of proximity discussions.

U.S. Air Force Col. Pat Ryder said the U.S. military has seen few airstrikes with the Russians launching artillery strikes instead.

“While we’ve seen no Russian airstrikes in the northern areas of Syria this week, it appears the Russians have conducted some airstrikes after all in southern Syria in the vicinity of Palmyra in support of the Syrian regime.”

If the Syrian army and its allies capture Palmyra, in the central province of Homs, it would be a major victory against IS militants in Syria.

“If the regime keeps the current momentum of its offensive, they can take Palmyra within days,” said Turkey-based activist Osama al-Khatib, who is originally from Palmyra. IS has built strong defenses in the town, including trenches around it, taking advantage of sandstorm earlier this week to launch counter attacks, said al-Khatib, speaking over the phone.

He said Syrian government forces were now about 10 kilometers (six miles) from the town.

According to two activist groups, the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees, warplanes conducted more than a dozen airstrikes since Friday morning. The Observatory said troops were slowly advancing toward Palmyra, adding that both sides were bringing in reinforcements. It said there were casualties on both sides but did not give any figures.

Syrian troops and their allies have been on the offensive in the area since last week and on Tuesday captured “Hill 900,” which is the highest point near Palmyra and overlooks the town, according to the Observatory.

A TV channel belonging to Lebanon’s Hezbollah group, which is allied with Syrian President Bashar Assad, said Syrian troops captured another hill just northwest of Palmyra on Friday. Hezbollah’s media arm known as Military Media showed footage from the battles, with helicopter gunships firing missiles in a mountainous, desert area.

Palmyra, home to famed Roman ruins, has been under the firm control of IS since the extremists captured it in May last year.

In October, The Associated Press obtained a video that showed the main structure of 2,000- year-old iconic Arch of Triumph in Palmyra has been destroyed. Activists have said that IS extremists blew up the arch.

IS also destroyed the Temple of Bel and the smaller Baalshamin temple last August. The Islamic State group considers such relics promote idolatry.

On Thursday, Putin said Moscow would keep enough forces in Syria to continue the fight against the Islamic State group, the Nusra Front and other extremist organizations. Russia will also continue to boost the Syrian military with weapons, training and operational guidance, Putin added.

The Russian campaign has helped turn the tide of war and allowed Assad’s forces to make significant advances ahead of peace talks, and established Russia as a major player in the diplomatic effort to determine Syria’s future.

Four Russian servicemen have been killed in action in Syria since Sept. 30, when Moscow began its aerial campaign. They dead include a pilot of a Russian plane downed by Turkey, a marine killed on a mission to rescue the pilot’s crewmate, a military adviser killed by shelling and a fourth man the circumstances of whose death haven’t been revealed yet. In addition, officials said one soldier at the Russian base killed himself.

The Aamaq news agency, affiliated with IS, claimed that its fighters killed a Russian military adviser near Palmyra this week, showing a video of a bloodied man in military uniform as well as an automatic rifle, telecommunication devices, a helmet and first aid kit with writings in Russian.

In Geneva on Friday, Bashar Ja’afari, the head of the government team and Syria’s U.N. ambassador, said the latest round of talks with the U.N. special envoy Staffan de Mistura was “useful” and focused on “fundamental principles” for a solution to the Syrian conflict that his side had presented.

Later in the day, the head of the Syrian opposition delegation, Asaad al-Zoubi, said his side is focused on achieving a “transitional governing body with full executive powers” for Syria.

De Mistura said an upcoming meeting between U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov could be “crucial” to help move toward a political transition in the country after five years of war.

Kerry is expected in Moscow next week.

The U.N. envoy also said he gave both sides homework for the weekend and that when talks continue on Monday, he will strive to reach a “minimum” platform between the government and the opposition teams.

De Mistura said he plans three additional rounds of talks, after which “we need to see concrete results.” He also urged the Syrian government to put forward a “paper” on transition, saying the opposition had already presented one.

Earlier Friday, the opposition said the Syrian government was “procrastinating” and not engaging in serious negotiations in Geneva.