BEIRUT (Reuters) - Government air raids struck more towns in rebel-held southwest Syria on Wednesday and knocked out hospitals overnight, a war monitor said, as a Russian-backed offensive gathered pace with no sign of Washington following through on a pledge to respond.

Warplanes targeted the towns of Dael and Saida for the first time since the assault began, and the U.N. Syria envoy Staffan de Mistura warned it could turn into a situation like the battles of eastern Ghouta and Aleppo combined.

President Bashar al-Assad has already driven rebels out of all areas near the capital Damascus this year and aims to restore control over rebel-held areas at the borders with Jordan and the Israeli-occupied Golan Heights.

The United Nations says the 10-day-old offensive has uprooted at least 45,000 civilians. Jordan, which already hosts some 650,000 Syrian refugees, has said it will not open the border for new refugees.

Government forces are thrusting into rebel areas with Russian support, despite warnings from Washington which brokered a “de-escalation” deal with Moscow to halt fighting in southwestern Syria last year. Washington has warned Assad of serious repercussions if he orders an assault, but there has been no sign of action to stop him.

The Observatory said the offensive had killed 47 people so far and the wider air strikes on Wednesday were forcing more people to flee. UOSSM, a medical charity that operates in the area, put the death toll at 68.

The International Committee of the Red Cross (ICRC) said it was “concerned about the safety of tens of thousands of civilians caught in the line of fire or fleeing violence in the southern governorate of Deraa”.

Northeast of Deraa, the pro-government forces captured three more villages on Wednesday, a military media service run by Assad’s ally Hezbollah reported, after capturing the nearby town of Busra al-Harir on Tuesday.

ASSAD STRENGTHENED

Assad and his allies are now in by far their strongest position since the early days of a seven-year civil war in which half a million people have been killed and more than half of all Syrians driven from their homes. Assad has vowed to reassert his control over every inch of the country.

Government forces have repeatedly been accused of striking medical facilities in opposition-held areas. Damascus and Moscow deny intentionally targeting them.

The Observatory said three hospitals were struck overnight in the towns of Saida, al-Jeeza and al-Musayfra near the Jordanian border to the east of Deraa city. UOSSM said that in addition to the three that were hit, a fourth hospital was shut after a shell fell nearby.

State-run TV station al-Ikhbariya said electricity to Deraa city - which is divided between rebels and the government - had been cut because “terrorist organizations” had targeted a power line in al-Musayfra, some 20 km (12 miles) to the east.

State television said about a thousand people, including hundreds of fighters, had agreed to accept government rule in Shaara, 60km (40 miles) to the north. It showed scores of them waving flags and chanting pro-Assad slogans.

The Hezbollah media service said hundreds of families had crossed front lines from Dael to government territory to escape rebel control.

The southwest is one of just two large areas of Syria still in the hands of rebels seeking to topple Assad, along with a region in the northwest near the Turkish border.

Washington’s sponsorship of the truce in the southwest is one of the highest-profile U.S. diplomatic initiatives in Syria since President Donald Trump took office.

Washington has told Free Syrian Army (FSA) rebels they should not expect military support against the offensive, according to a message sent to rebel commanders seen by Reuters.