Syria’s rebel factions will be “disbanded”, the head of the group that led the ousting of Bashar al-Assad has pledged, as he seeks to reassure minorities at home and abroad that the country’s interim leaders will protect all Syrians, as well as state institutions.

Ahmed al-Sharaa, the leader of the Hayat Tahrir al-Sham (HTS) group that toppled Syrian president Assad, said all rebel factions would “be disbanded and the fighters trained to join the ranks of the defence ministry” during a meeting with members of the minority Druze community.

“All will be subject to the law,” he added, according to posts on the group’s Telegram channel. He also emphasised the need for unity in the multi-ethnic and multi-confessional country.

“Syria must remain united,” he said. “There must be a social contract between the state and all religions to guarantee social justice”.

In a separate meeting with a British delegation, Sharaa, who was formerly known by his nom de guerre, Abu Mohammed al-Jolani, also said that international sanctions against Damascus must be lifted if refugees displaced by the war are to return.

He spoke “of the importance of restoring relations” with London, and stressed “the importance of ending all sanctions imposed on Syria so that displaced Syrians … can return to their country”.

After Assad’s fall last week, European countries including the UK, Germany, France, Italy, Sweden and Norway among others said they were suspending the processing of asylum applications from Syrians, despite the lack of clarity about what lies ahead for the country, which remains fractured, with hardline Islamic State fighters still operational in parts of the east.

The US and the EU had placed wide-ranging sanctions on the Assad regime, including bans on weapons sales to Syria and oil imports from the country and a ban on investment in its oil industry.

The sanctions have played a part in crippling the war-torn country’s economy; hyper inflation is rampant and at least 70% of the population live in poverty.

Assad’s fall has left western countries with the dilemma of how to deal with HTS, which has its roots in al-Qaida. HTS maintains it has renounced the group’s extreme ideology, yet it has been accused of human rights abuses and remains proscribed as a terrorist group by the UN and several western countries, including the US and UK. Sharaa’s meetings with foreign delegations and statements on protecting minorities are seen as an attempt to show his faction deserves to be taken off “terror” lists.

The EU’s foreign policy chief, Kaja Kallas, said on Tuesday that the bloc would send an ambassador back to Damascus. “We are ready to reopen our delegation, which is the European embassy, and we want this to be fully operational again,” she said.

Kallas added that the EU would aim to help authorities restore basic services like electricity, water and infrastructure. She warned, however, of the risk of a resurgence by hardline IS militants, an enemy of HTS.

“The lack of predictability demands utmost caution. The risk of a Daesh [IS] resurgence, particularly in eastern Syria, is real. We cannot let this happen,” she said.

France also raised a flag on Tuesday over its embassy in Damascus after it had been closed for 12 years, the foreign ministry said.

The decision by many European governments to suspend processing asylum applications has been greeted with dismay by Syrian refugees, many of whom are fearful of returning to their country of birth and who have built new lives in their adopted countries.

In Germany, which took in nearly 1 million refugees during the war and which is now home to Europe’s largest Syrian diaspora, the opposition CDU party – expected to win elections early next year – has already begun calling for Syrian refugees to be returned to their homeland.

In the UK, the home secretary, Yvette Cooper, has said the government was monitoring the situation, which she described as “very unstable at the moment”. Refugee advocates have called the decision to suspend processing of applications “cruel”.

The comments came shortly after Assad broke his silence for the first time since fleeing Syria to Russia, claiming he had been evacuated from a military base at Moscow’s request. Russia, along with Iran and Lebanon’s Hezbollah, helped prop up Assad’s rule.

“My departure from Syria was neither planned nor did it occur during the final hours of the battles, as some have claimed,” said a statement from Assad on the ousted presidency’s Telegram channel.

“Moscow requested that the base’s command arrange an immediate evacuation to Russia,” he added.

“When the state falls into the hands of terrorism and the ability to make a meaningful contribution is lost, any position becomes void of purpose.”

Agence France-Press and Reuters contributed to this report