The United Nations refugee chief said Saturday that some 200,000 refugees have returned to Syria from neighbouring countries since the government of Bashar Assad was overthrown last month.

The influx comes after an estimated 300,000 refugees returned from Lebanon late last year while it was under bombardment during the Israel-Hezbollah war.

Many more who had fled during the country's nearly 14-year uprising-turned-civil war are thinking about going back soon.

However, UN High Commissioner for Refugees Filippo Grandi cautioned during a visit to Damascus during which he met with Syria's new de facto leader, Ahmad al-Sharaa, that many of the returnees may not stay unless living conditions in the country improve.

"In order to make this return sustainable and to make life better for all Syrians the economy needs to return, services need to be restored and reinstated, security needs to be guaranteed and housing needs to be the subject of a very important reconstruction program," Grandi said.

He called for the lifting of Western sanctions on the country, many of which targeted Assad's government but have not been removed since it fell on December 8 as the result of a lightning rebel offensive. "Sanctions are an important obstacle for the return of refugees," Grandi said.

There are more than 4.7 million refugees registered with the UN refugee agency, or UNHCR in neighbouring countries. The largest number are in Turkey, with nearly 2.9 million, followed by Lebanon, with more than 755,000.

In addition to returning refugees, some 600,000 out of an estimated seven million internally displaced Syrians have gone home, Grandi said.

Some of those returns may be controversial.

Kurdish authorities in the country's northeast are preparing to release some Syrian detainees in the sprawling al Hol camp that houses family members of suspected Islamic State group members, allowing them to return to their home areas.