BEIRUT (AP) -- The Syrian search-and-rescue group featured in an Oscar-winning documentary announced that one of its volunteers had been killed by government artillery fire in the city of Homs Tuesday, as pro-government forces reached the outskirts of Islamic State-held Palmyra in the center of the country.
The Syrian Civil Defense outfit, popularly known as the White Helmets, was honored with an Oscar on Sunday as the subject of a Netflix documentary about the group's harrowing mission.
The group announced that one of its volunteers Muhammad Dabdoub was killed in the line of duty by government artillery fire in Homs, Syria's third-largest city. Dabdoub was the 164th White Helmets rescuer killed in the war.
Dabdoub was serving in al-Waer, the opposition's last foothold in Homs. The neighborhood is besieged by government forces and exposed to shelling and bombardment daily, despite a cease-fire agreement that is supposed to facilitate talks between the government and opposition in Geneva.
U.N. mediator Staffan De Mistura has said he believes the truce has largely held.
But the media arm of Hezbollah, the Lebanese militant group that has sent thousands of fighters in defense of the Syrian government, boasts regularly on social media of government strikes against al-Waer and advances on the opposition-held neighborhood of Qaboun, in Damascus.
The Washington-based Seige Watch monitoring group says 75,000 people are trapped in al-Waer. Many are displaced from other parts of Homs. Rights groups such as the New York-based Human Rights Watch have accused the government of using violence to displace populations it sees as unfavorable to its rule.
Syrian talks in Geneva are moving at a glacial pace with a series of bilateral meetings between the United Nations envoy and the conflicting sides in a bid to get them to sign off on a process of dialogue focused on governance, elections and re-drafting the constitution.
The Damascus delegation has insisted on putting the fight against terrorism at the top of the agenda, a move rejected by the opposition as an effort to stall talks on the sensitive issue of political transition.
Both sides accuse the other of keeping up the violence.
In central Syria, government forces and their allies from Hezbollah reached the southwestern gateway of Palmyra, located about 5 kilometers (3 miles) from its famed Roman ruins, according to the activist-run Palmyra Coordination Committee.
The activist group reported airstrikes across the town Tuesday morning. The Britain-based Syrian Observatory for Human Rights and Hezbollah's media outlets also reported the advances.
It was the second campaign against IS in Palmyra in the past year. The government lost control of Palmyra in December, less than one year after reclaiming it from IS with Russian support.
The town, according to Mohammed Homsi, the director of the activist-run Palmyra News Network, is almost entirely deserted. Islamic State fighters evacuated the last of their relatives on Sunday. Pro-government forces are stationed on the hilltops overlooking Palmyra from two sides and could retake the town within "days or hours," Homsi predicted.
When the militants moved in, there were only 300 families left in the town, after the Syrian authorities evacuated their families in the days before, said Homsi.
Archeologists have decried what they say is extensive damage to the town's famed ancient ruins.
Palmyra was Syria's top tourist attraction before war gripped the country in 2011, drawing tens of thousands of visitors each year. Syrians affectionately refer to the town as "the bride of the desert."
Drone footage released by Russia's Defense Ministry earlier this month showed new damage to the facade of Palmyra's Roman-era theater and the adjoining Tetrapylon - a set of four monuments with four columns each at the center of the colonnaded road leading to the theater.
A 2014 report by a U.N. research agency disclosed satellite evidence of looting while the ruins were under Syrian military control. Opposition factions have also admitted to looting the antiquities for funds.
Meanwhile in New York, Russia and China on Tuesday vetoed a Western-backed U.N. draft resolution that would have imposed a new set of sanctions against Syria over its government's alleged involvement in chemical weapons attacks. Speaking shortly before the U.N. vote, Russian President Vladimir Putin said the sanctions would be "utterly inconsequential" and could hamper the Syria peace talks which are currently under way in Geneva.
The draft U.N. resolution, initially sponsored by Britain and France who were joined by the United States, would have imposed sanctions on 21 Syrian individuals, organizations and companies allegedly involved in chemical attacks. It would also have banned all countries from supplying Syria's government with helicopters, which investigators have determined were used in chemical attacks.
In Geneva, the office of U.N. Secretary General Antonio Guterres said it was "extremely concerned" about the welfare of more than 400,000 people trapped in a government siege of the Ghouta suburbs of the capital, Damascus.
Stephane Dujarric, spokesman for Guterres, said U.N. relief convoys have been blocked from accessing the area since October 2016.
"Civilians currently have limited access to critical food, health, and nutrition assistance," Dujarric said.
Associated Press writers Dominique Soguel in Geneva and Vladimir Isachenkov in Moscow contributed to this report.