BEIRUT - Regime troops were locked in heavy fighting Tuesday with the Islamic State group in central Syria, where they dealt the militants a major blow by seizing the ancient city of Palmyra.

Just two days after seizing Palmyra from IS, pro-government fighters advanced southwest towards the militant-held town of Al-Qaryatain, the Syrian Observatory for Human Rights said..

They captured a series of strategic hilltops overlooking the town, said the Britain-based monitor, backed by "intense" air strikes by both Syrian and Russian warplanes.

State news agency SANA said the army, backed by pro-government militia, had also seized rural farmland south of Al-Qaryatain as they closed in on the town.

China said Tuesday it has appointed its first special envoy to Syria, as part of efforts to increase its diplomatic footprint in the Middle East.

China depends on the volatile region for oil supplies but has long taken a back seat in its disputes, only recently beginning to expand its role. One analyst said the appointment was a calculated move.

In recent months Beijing has hosted high-level delegations from both the Syrian government and the opposition.

IS had seized the strategic town in August 2015, kidnapping at least 230 people, including dozens of Christians, and razing its famed Mar Elian monastery.

The town lies on a key road linking Palmyra with the Qalamun region of Damascus province to the west.

Sunday's capture of Palmyra, known as the "Pearl of the Desert" for its colonnaded alleyways and stunning temples, was seen as a the biggest blow so far in the war against IS in Syria. Syria's government has hailed the victory as proof of its credentials in the anti-IS fight.

On Tuesday, Defence Minister Fahed Jassem al-Freij said the armed forces would push their offensive against IS to secure a "final victory" over the militants, the SANA state news agency reported.

"Bringing security and stability to Palmyra is an essential step towards a final victory over takfiri (extremist Sunni Muslim) terrorism," Freij told his Iranian counterpart Hossein Dehghan.

Syria's armed forces have pledged to strengthen their hold on Palmyra and press on towards IS's northern bastion in Raqa as well as the oil-rich province of Deir Ezzor to the east.

The militants swept into Palmyra, a UNESCO-listed World Heritage Site, in May 2015 and began a campaign to destroy tombs and shrines it considers idolatrous.

The extremist group demolished the 2,000-year-old temple of Bel and also blew up the Arch of Triumph.

IS also used Palmyra's ancient theatre as a venue for public executions and murdered the city's 82-year-old former antiquities chief, Khaled al-Assaad.

Syria's head of antiquities, Maamoun Abdulkarim, told AFP that 80 percent of the site was still "in good shape" and the ancient ruins could be restored in five years with UNESCO's help.

But UN expert Annie Sartre-Fauriat, who belongs to a group of experts on Syrian heritage set up by UNESCO in 2013, said she was "very doubtful" that would be possible.

As they retreated from Palmyra at the weekend, IS fighters planted roadside mines near some of the most celebrated ruins of the city.

Syrian army sappers have already defused dozens of the makeshift bombs and have conducted controlled detonations of others, a military source told AFP.

On Tuesday, Moscow dispatched a group of Russian deminers, sniffer dogs, and advanced radar equipment to help the Syrian army secure Palmyra, Russia's state media channel Pervy Kanal reported.

Moscow began its air war in support of President Bashar al-Assad's troops in September, carrying out strikes on "terrorist" targets across the country.

Earlier this month Russia announced a drawdown but it said it would keep up its support for the regime's battle against IS and other militants groups.

Analysts say that only 10-25 percent of Russian forces have left Syria since President Vladimir Putin announced the withdrawal.

"All the talk in the West that Russia was going to ditch Assad was nonsense," said Pavel Felgengauer, a Russian military analyst.

"We are not planning to abandon him now. Russia wants Assad to stay in power and the goal is to give him a chance to win the civil war."

Meanwhile, wealthy countries have resettled only a fraction of the nearly five million refugees who have fled Syria, Oxfam said on Tuesday, urging them to step up and do their share.

The British charity called on wealthy countries to resettle at least 10 percent of the 4.8 million Syrian refugees registered in the region surrounding the war-ravaged nation by the end of the year.

So far, rich countries have pledged few than 130,000 resettlement spots, and only around 67,100 people - a mere 1.39 percent of the refugees - have made it to their final destinations since 2013, Oxfam said.

The charity issued its report ahead of an unprecedented UN-hosted conference in Geneva on Wednesday, where countries will be asked to pledge resettlement spots for Syrian refugees.

As the brutal conflict enters its sixth year, most of the people who have fled are located in Syria's immediate neighbours such as Turkey, Lebanon, Jordan and Iraq.

But as the war has dragged on and conditions have worsened in the surrounding states, Syrians have increasingly set their sights on Europe, accounting for most of the more than one million migrants who risked their lives crossing the Mediterranean last year.

They are also believed to be heavily represented among the more than 7,500 people, including many children, who have died trying to make the crossing since 2014.

Wednesday's conference, which will be opened by UN Secretary General Ban Ki-moon, will aim to ensure "global responsibility sharing" for the crisis sparked by Syria's brutal conflict, which has claimed more than 270,000 lives.

"To date the response to calls of increased resettlement of vulnerable refugees has been disappointing, and the conference is an opportunity for states to mark a change of course," the Oxfam report said.

The charity said its analysis showed only three of the world's wealthy countries - Canada, Germany and Norway - had pledged more resettlement spots than what was considered their "fair share" according to the size of their economies.

Five other countries, Australia, Finland, Iceland, Sweden and New Zealand had meanwhile pledged more than half of their fair share, while the remaining 20 nations included in the analysis fell far short, Oxfam said.

Thus, France had only so far pledged to take in 1,000 Syrian refugees, or only four percent of the nearly 26,000 considered to be its fair share, the report said.

The United States, which has resettled 1,812 Syrian refugees and said it will take in 10,000 more, has meanwhile pledged just seven percent of the nearly 171,000 considered to be its fair share, it showed.

The Netherlands also stood at seven percent, Denmark at 15 and Britain at 22, Oxfam said.

"We need to show Syrian people that 'solidarity' is an action, not a sound-bite," Oxfam chief Winnie Byanyima said in a statement.

"Countries with a strong economy, good services and developed infrastructure can immediately resettle 500,000 refugees between them - if they chose to," she said.

Byanyima said that in Lebanon, one in five inhabitants is a Syrian refugees, while they constitute 10 percent of the population in Jordan, which counts a refugee camp as its fourth largest "city".

"These countries have fragile economies and weak infrastructure. They can no longer shoulder this responsibility virtually alone," she said, insisting that the Geneva conference "should result in urgent solutions, offering people safe and legal routes to a welcome in third countries".