It would be impossible for Britain to conduct a mass airlift of its nationals from Russia, but the UK government is planning for “all scenarios” after the country pulled back from the brink of civil war, the UK foreign secretary has said. James Cleverly said he could not give an accurate figure for the number of Britons still in Russia, although the UK government is understood to believe the number is in the “single thousands”. As he provided an update in parliament, Cleverly was urged to create a register of UK nationals in case they needed to be evacuated. Concerns about their plight came after Wagner group mercenaries apparently marched on Moscow in defiance of Vladimir Putin’s leadership. These concerns are also understood to have been a reason for convening the UK government’s Cobra emergency response committee on Thursday. Addressing MPs on Monday, Cleverly responded to calls by Alicia Kearns, the chair of the foreign affairs select committee, for the government to create a register of Britons in Russia. “We of course look at scenario planning to make sure we are able to respond to whatever happens. But we don’t force British nationals to register with the embassy so therefore it is not possible for us to give accurate figures,” he said. He reiterated UK travel advice, which has been in place for several years, against travel to all parts of Russia and said UK citizens should consider leaving unless their presence was absolutely necessary. But he told Kearns that the ability of the UK to conduct an extraction operation as it did earlier this year in Sudan – when British troops landed there as the country descended into civil war – “would be severely limited, probably to the point of impossibility”. Responding more broadly to the events of last week in Ukraine and Russia, Cleverly was careful in choosing his words when it came to questions about potential regime change in Russia. “The question of the leadership of Russia is one for the Russian people, but they will now see how very badly they have been led,” he said. He was also urged by the former prime minister Liz Truss to make sure “we have a plan in the case of the implosion of Russia” and that Ukrainian membership of Nato was fast-tracked at the forthcoming Nato summit in Lithuania. He told her that “however long that Nato membership would otherwise have taken, it should of course now be truncated”. For Labour, the shadow foreign secretary, David Lammy, reiterated that “all sides” of the Commons would support Ukraine for the long haul and asked if the Wagner group’s founder and leader, Yevgeny Prigozhin, “would now disappear into obscurity” or if his presence, potentially in Belarus, could pose a new threat to Ukraine from that direction. Cleverly said the UK had made it clear from the start of Russia’s invasion of Ukraine that any action by Belarus to get involved in the conflict would be met with “severe repercussions from the UK” and a sanctions package was also in place in relation to Russia’s ally.