Britain has imposed sanctions on Belarus's potash and petroleum product exports in an attempt to put pressure on President Alexander Lukashenko, who swiftly retorted that London should "choke on" the new measures.

So far Western sanctions have done little to persuade Mr Lukashenko, in power in the former Soviet republic since 1994, to change course from a crackdown on his political opponents.

The US also announced that it will impose fresh sanctions, with President Joe Biden expected to sign an executive order today.

The British sanctions also include measures to prevent Belarusian air carriers from overflying or landing in the United Kingdom and a prohibition on the provision of technical assistance to Mr Lukashenko's fleet of luxury aircraft.

State-owned Belaruskali is the world's top potash producer and accounts for a fifth of global potash trade.

"These sanctions demonstrate that the UK will not accept Lukashenko’s actions since the fraudulent election," Foreign Secretary Dominic Raab said.

"The Lukashenko regime continues to crush democracy and violate human rights in Belarus."

"The products of Lukashenko’s state-owned industries will not be sold in the UK, and our aerospace companies will not touch his fleet of luxury aircraft."

Asked about the sanctions, Mr Lukashenko said Britain should choke on the sanctions.

"You are America's lapdogs," he said of Britain.

Today marked the first anniversary of an election which opponents said was rigged to let Mr Lukashenko win.

Tens of thousands of people took to the streets in the biggest challenge to his rule since he became president in 1994.

He says he won the election fairly and responded with a crackdown on opponents in which many have been arrested or gone into exile abroad.

"These measures represent a significant additional step in bringing pressure to bear on the Lukashenko regime," Britain's foreign ministry said.

"They are carefully targeted to build pressure on Lukashenko, state institutions and those around him to change behaviour, while minimising, as far as possible, any unintended consequences on the wider population in Belarus."

EU sanctions designed to punish Mr Lukashenko for the crackdown will leave him largely unscathed and able to continue financing the economy and his security forces, rating agencies and analysts say.

Belaruskali also looks to face no major threat from the EU sanctions, analysts said.

The US sanctions will target key institutions and supporters of Mr Lukashenko including the Belarusian National Olympic Committee, business leaders and companies such a private Belarusian bank.

Also on the list is Belaruskali, which is alleged to be a source of illegal wealth for the regime.

Belarus leader denies involvement in activist death

President Lukashenko has denied his country's security services were involved in the death of an activist in Ukraine.

"He was a nobody for us," he said at a press conference in Minsk, adding that the death of exile Vitaly Shishov in Kiev last week had strained relations with Ukraine.

Kiev opened a murder probe and Lukashenko's critics accused his regime of killing the 26-year-old activist who helped his compatriots flee repression.

"What kind of madman would go and hang him?" Mr Lukashenko said, adding that he had "enough people to deal with without Shishov".

He accused Kiev security services of backing Mr Shishov and demanded Ukraine "put the facts on the table".

"Tell us what happened to the citizen of Belarus," he said.

Mr Shishov headed the Belarusian House in Ukraine, a non-governmental organisation involved in everything from helping fellow compatriots settle in Ukraine to staging anti-regime protests.

Mr Lukashenko also denied that Minsk tried to forcibly bring home athlete Krystsina Tsimanouskaya from the Tokyo Olympics, accusing her of being "controlled" by Poland, where she has since sought refuge.

"She would not have done this if she wasn't controlled by her mates in Poland," he said.

He added that there had not been "not a single" KGB agent at the Tokyo Olympics.