Russian diamond imports to the UK will be banned in the latest sanctions following the invasion of Ukraine.
Imports of Russian-origin copper, aluminium and nickel will be blocked, under legislation to be introduced later this year.
Rishi Sunak said the UK must show “violence and coercion do not reap rewards” ahead of the G7 summit in Hiroshima.
The Russian diamond industry was worth $4bn (£3.2bn) in exports in 2021.
The UK government said it was also planning to target 86 more people and companies connected to President Vladimir Putin, including people who are “actively undermining the impact of existing sanctions”.
Since Russia’s attack on Ukraine, the UK has targeted more than 1,500 individuals and entities and frozen more than £18bn assets under the sanctions regime.
Last year the UK, US, Canada and Japan banned imports of Russian gold in an effort to hit the country’s ability to fund the war in Ukraine.
Downing Street said more than 60% of President Putin’s war chest has been “immobilised” – worth about £275bn.
Both the US and the EU have announced similar sanctions on Russia – with US President Joe Biden setting out plans to ban Russian diamonds, seafood and vodka last year.
Mr Sunak is in Hiroshima for the first day of the G7 summit of some of the world’s richest nations.
The prime minister will visit the site of the first nuclear bomb detonation at the Hiroshima Peace Park alongside other G7 leaders before the meeting where the Ukraine war and economic security are likely to be high on the agenda.
Russia has significantly increased the frequency of its missile attacks on Ukraine recently, while Ukraine appears to be shooting down more of Russia’s missiles.
At the meeting, Mr Sunak is expected to warn other world leaders “against complacency in defending our values and standing up to autocratic regimes”.
On Sunday, he will meet the prime minister of India, Narendra Modi, who is attending the G7 summit as a guest.
Mr Modi has remained neutral on Russia’s invasion of Ukraine, calling for peaceful dialogue to end the conflict.
Mr Sunak told reporters travelling with him in Japan that he had seen “positive” steps from India in its stance on the war.
The prime minister said the sanctions demonstrated the G7 was unified in the face of the threat from Russia.
He said: “We are meeting today in Hiroshima, a city that exemplifies both the horrors of war and the dividends of peace.
“We must redouble our efforts to defend the values of freedom, democracy and tolerance, both in Ukraine and here in the Indo-Pacific.”