The Prime Minister has said the UK is “on the side” of the pro-democracy Belarusian opposition leader.
Boris Johnson welcomed Sviatlana Tsikhanouskaya to Downing Street as international pressure continues to mount on the Minsk regime.
Ms Tsikhanouskaya said she was sure there will be further help from the British Government for the people of Belarus.
The autocratic government of Alexander Lukashenko has faced added scrutiny in recent days following the treatment of Olympic sprinter Krystsina Tsimanouskaya, and the death of activist Vitaly Shishov in Ukraine on Tuesday.
Ms Tsikhanouskaya said she understood she could “disappear at any moment”, but added if this happened, the “movement” she had started “will continue without me”.
At the Downing Street meeting, Mr Johnson said: “We are very much on your side, very much in support of what you are doing. We are committed to supporting human rights and civil society in Belarus.”
He added: “We strongly support you, strongly support Belarus, the Belarusian people and I think we were among the first to put in sanctions after the hijacking of Roman Protasevich, the flight that was diverted.”
Outside Number 10, Ms Tsikhanouskaya was asked by reporters if she thought concrete help would be offered by the UK Government following the meeting with Mr Johnson.
“I am sure,” she replied.
The Belarusian opposition leader also said it was too early to comment on the death of Belarusian activist Mr Shishov in Ukraine.
The leader of the Kyiv-based Belarusian House in Ukraine was found hanged in one of the city’s parks not far from his home, police said in a statement.
A murder probe has been launched, with police believing that the death was made to look like suicide.
Ms Tsikhanouskaya added: “I understand you know, I can disappear at any moment. I understand this, but I should do what I am doing.
“I can’t stop, because I feel responsibility for the future of my country, the same as all those Belarusians felt fighting the government, feel their responsibility.
“But I know that even if I disappear one day, this movement will continue without me.”
Opposition leader Ms Tsikhanouskaya also met US President Joe Biden last week, as part of a tour to move Belarus up the agenda for Western countries.
Ahead of the visit to Downing Street, Belarusians living in the UK and human rights campaigners demonstrated outside the Foreign Office in Westminster.
Ken McBain, a UK representative of the human rights organisation Libereco, said the demonstration was about “highlighting what’s happening in Belarus in the last two days”.
He added: “There’s been a lot going on with the Olympics and then with a Belarusian activist in Kyiv – murdered it looks (like).
“We’re trying to show the British Government that more needs to be done. We cannot leave Lukashenko to do what he is doing to the country.”
Earlier this week, the treatment of Belarusian Olympic athlete Tsimanouskaya focused attention on the country.
Tsimanouskaya has been granted a visa by Poland after saying she feared for her safety at the Tokyo Games, claiming her team’s officials in Japan tried to force her to fly home.
The drama unfolded after Tsimanouskaya hit out at how officials were managing her team – setting off a massive backlash in state-run media in Belarus, where the authorities relentlessly crack down on government critics.
Tsimanouskaya told the BBC World Service: “It’s definitely not safe in Belarus and maybe I will only be able to return there after five or 10 years.”
Belarus held elections on August 9 last year, in which Mr Lukashenko was declared the victor.
The result was followed by huge street protests and claims by opponents of the regime and Western governments that the elections were rigged.
Ms Tsikhanouskaya fled to Lithuania after the election in fear for her own safety.
After the meeting with Ms Tsikhanouskaya, a Downing Street spokesperson said: “The Prime Minister outlined the steps the UK has taken to hold the regime to account, including placing sanctions on Lukashenko himself.
“He stressed the UK’s commitment to the Belarusian people, in particular through tripling our financial support to Belarusian civil society this year.”