Jordan confirmed that 422 people were evacuated from Syria on Saturday to be resettled abroad
Several hundred Syrian rescuers remain trapped in the country's south, with no prospect of escape from approaching government troops, two of them said on Monday after many of their colleagues were secretly evacuated.
Israel on Sunday helped more than 400 people - White Helmet rescue workers and their families - flee a neighbouring pocket of southwestern Syria as government forces bore down on them.
They were then taken to Jordan and will be resettled to Western nations including France, Britain, Germany, and Canada.
"It was the only alternative for our trapped volunteers who would otherwise have faced detention or death at the hands of the Syrian regime and its ally Russia," the group said on Monday.
Ninety-eight male and female White Helmet volunteers were able to escape to Jordan with 324 members of their families, it said in a statement.
But a similar number remain trapped in southern Syria.
"We're calling on concerned parties to help us leave," said Cesar, a 23-year-old White Helmets worker in the southern city of Daraa.
He estimated some 400 fellow rescuers were still in the provinces of Daraa, bordering Jordan, and Quneitra, next to the buffer zone abutting the Israeli-annexed Golan.
Cesar said he had learned of the operation a few days ago "by chance", but when he contacted the White Helmets' leadership, they told him it was too late to register to leave.
'Made things worse'
"They set up another meeting for today on the subject, but we found out a little while ago that the efforts failed. The fact that some White Helmets members left and some stayed hurt us more than it helped us," he told AFP on Monday.
"Yesterday's evacuation through Israel only made things worse. We're afraid of the regime and Russia's reactions."
Russian-backed Syrian forces have been battering the south for more than a month in a bid to bring it back under government control.
The military push has damaged hospitals and civil defence centres, pushing hundreds of thousands to flee towards the Jordanian and Israeli borders, which remained sealed.
The foreign ministry in Damascus slammed the evacuation on Monday, calling it a "criminal operation" and repeating its accusation that the White Helmets were a front for "terrorists".
Moscow said it was "symbolic that the White Helmets preferred to flee Syria thanks to the foreign support, thus revealing their true nature".
The 422 people evacuated will be allowed to stay in Jordan for three months before being resettled, Amman has said.
On Monday, the White Helmets called on the international community to help those left behind in southern Syria.
"We thank all governments who contributed to the success of this operation to rescue the rescuers, and we ask that they do more to help the hundreds of thousands remaining in southern Syria," they said.
White Helmets chief Raed Saleh said not all workers had been evacuated because some had not signed up to do so, while "some volunteers were not able to reach the evacuation point".
He said there were no plans for a second operation.
"They pulled out the others but can't get us out?" asked 20-year-old rescuer Imad from a rebel village in Quneitra.
"We're surrounded," he said.
Imad also said there had been a meeting of White Helmets officials in Jordan on Monday to discuss the fate of the remaining rescuers.
After the meeting, the White Helmets members still in Syria were told their only option was to be bussed north to opposition-controlled territory under a surrender deal.
Last week, rebels in Quneitra agreed with Russia to give up their remaining territory in the province in exchange for an end to bombardment and safe passage to other rebel-held territories.
The terms are similar to previous deals that have helped to bring swathes of Syria under government control.
But Imad told AFP he feared reprisals.
"We're a burnt card when it comes to the Syrian army - there won't be any mercy. Whoever the regime gets its hands on is lost, and no one knows what ends up happening to them," he said.
Founded in 2013, the Syria Civil Defence, or White Helmets, works to rescue those wounded by attacks in rebel-held territory.
The White Helmets have rescued thousands of civilians trapped under the rubble or caught up in fighting in battered opposition-held zones along various fronts of Syria's seven-year conflict.
The group's motto - "To save one life is to save all of humanity" - is drawn from a verse in the Quran, although the White Helmets say they help all victims, regardless of religion.
Some members have received training abroad, including in Turkey, and returned to instruct colleagues on search-and-rescue techniques.
The group receives funding from a number of governments, including Britain, Germany and the United States. It also solicits individual donations to purchase equipment such as its signature hard hats.