Militants have killed almost 50 Syrian regime fighters in 48 hours, a monitor said on Saturday, in some of the deadliest attacks on pro-Damascus forces in recent weeks.

Kurdish-led forces in March announced the defeat of the Daesh militant group’s territory in eastern Syria, but the militants have retained hideouts there and in other parts of the country as well as the ability to carry out deadly assaults.

Since Thursday, Daesh militants have killed 35 pro-Damascus fighters in regime-held parts of central and eastern Syria, the Syrian Observatory for Human Rights said.

Observatory chief Rami Abdel Rahman described those attacks as producing “the highest death toll among regime forces since the area was declared defeated” in the eastern village of Baghouz last month.

Meanwhile, regime fighters also came under attack on another front of Syria’s grinding eight-year war, the Britain-based monitor added.

On Saturday, militants linked to Syria’s former Al Qaeda affiliate attacked loyalist checkpoints and positions on the western edges of the northern city of Aleppo, killing 13 more pro-Assad fighters, it said. Attacks by the militants have killed 27 troops and allied militiamen, including four senior Syrian army officers, in the desert east of Homs province since Thursday, the Observatory said.

The propaganda arm of Daesh said its fighters carried out the operation.

The Observatory also said Daesh fighters killed another eight soldiers and militiamen, including two officers, in the eastern province of Deir Al Zor on Thursday night.

That attack targeted a desert village south of the city of Mayadeen on the Euphrates River, upstream from the village of Baghouz where Daesh made a desperate last stand in March.

The Observatory said Saturday’s attack by the Syria’s former Al Qaeda affiliate, Hayat Tahrir Al Sham (HTS)-linked Abu Bakr Al Sadeeq Army on the western edges of Aleppo city came after regime bombardment overnight hit eastern and southeastern parts of the Idlib region.

A planned buffer zone around the region was never fully implemented as militants refused to withdraw from it.

Syrian President Bashar Al Assad on Friday called for progress on a stalled buffer zone deal around Idlib region ahead of fresh talks aimed at ending his country’s eight-year war.

Assad met envoy Alexander Lavrentiev from key ally Russia in Damascus to discuss the negotiations due April 25-26 in Kazakhstan.

Assad insisted at the meeting Friday that “obstacles” blocking the full implementation of the deal be removed,” the presidency wrote on Facebook.

He said the main aim of the accord was to “eliminate terrorist groups,” as militants have failed to pull out of the specified areas.

The UN has expressed concern over escalating violence in Idlib, warning that the flare-up is threatening aid deliveries to some 2.7 million people in need.

More than 86,500 people fled their homes in February and March as a result of the surge in violence, it said.

Assad has managed to claw back some two thirds of the country since Russia launched a military intervention in 2015, but Idlib remains beyond regime control.

Syria’s Al Watan newspaper reported that Lavrentiev had delivered to Assad a “positive Saudi initiative” after visiting the kingdom, but gave no further details.

Syrian officials made no comment on the report.

Several Russian envoys met Assad and discussed a constitutional committee, trade, as well as the ways to improve Syria’s relations with neighbouring Arab countries, Russia’s Foreign Ministry said.

Formation of a constitutional committee is key to political reforms and new elections meant to unify Syria.

Syria’s opposition last year agreed to join the process of rewriting the constitution under U.N. auspices following a peacemaking conference in the Russian city of Sochi.

The Foreign Ministry said in a statement late on Friday that Assad met Russia’s Syria envoy Alexander Lavrentiev, Deputy Russian Foreign Minister Sergei Vershinin and several Russian Defence Ministry officials.

Separately, Interfax news agency, citing the Russian government, said Russian Deputy Prime Minister Yury Borisov would meet Assad in Damascus later on Saturday to talk about cooperation in trade and economy.

Agencies