Five protesters were arrested after trying to approach Chinese Premier Wen Jiabao during a Free Tibet group demonstration.
Several people vaulted barriers as he arrived outside the Chinese Embassy in London amid a noisy demonstration.
Supporters had greeted Mr Wen with dragon dancers and firecrackers as he visited as part of his UK tour.
Conservative leader David Cameron had earlier raised human rights issues during a 45-minute meeting with Mr Wen.
The discussions, attended by shadow cabinet members William Hague and George Osborne, focused on economic issues such as the importance of avoiding protectionism and deepening trade links.
Mr Cameron said: "I also raised with Premier Wen the issue of human rights in China and greater participation in the political process, including at a time of economic difficulty, and our wish to see a continuing dialogue on these issues."
In recent months, thousands of Tibetan people have been killed and imprisoned
They talked about the importance of a united international response to prevent Iran from acquiring nuclear weapons, he added.
After the meeting, Mr Wen travelled to the Chinese Embassy where a group of around 100 were chanting pro-Tibetan slogans.
From behind barriers, they brandished placards reading "Stop Killing in Tibet" and posters featuring Mr Wen underneath a "Wanted" sign.
BBC correspondent Barnie Choudhury said Mr Wen took no notice of the protest as he made his way into the building.
"A dozen or so protesters vaulted over the barriers and made their way across the road," he said.
"Police decided they had to go in and began trying to hold the protesters back as they tried to breach the barriers."
Wen Jiabao also met Prime Minister Gordon Brown during the visit
Officers were filmed taking several people away in handcuffs, although our correspondent said they were later allowed to rejoin the protesting crowd.
The Metropolitan Police confirmed five men had been arrested on suspicion of breach of the peace.
One protester told the BBC: "We are here to support our people in Tibet. In recent months, thousands of Tibetan people have been killed and imprisoned."
Tibetan Ugyan Norbu, who has lived in Britain for 30 years, said: "Tibet is caged and has been for 50 years. Tibetan people cannot go in or out. They live in terror of the Chinese authorities.
"We have to come here and demonstrate."
Mr Wen's European tour, which includes three days in Britain, takes in Germany and Spain.
He has also visited the EU headquarters in Brussels and the World Economic Forum in Davos.
He will also make a speech at the University of Cambridge, the Chinese Foreign Ministry said.
BBC News correspondent Jill McGivering said Mr Wen is expected to promote China's economic prospects and push for more investment from the UK.
She said: "These are troubled times - and Britain and China are sticking together.
"Gordon Brown sees China as a powerful ally as he presses for reform of international financial bodies.
"And China's economy - expected to grow at about 7% this year - is very attractive to British investors."
She added that Mr Wen would be seeking reassurance that the UK will join China's fight against global protectionism.
This is when governments restrict import quotas in a bid to protect domestic industries from global competition - but China says this is damaging to its export trade.
The visit follows an announcement earlier this month by Foreign Secretary David Miliband that improving relations with China is to be a "major priority" for the UK in the years ahead.
In a 20-page framework document Mr Miliband said the UK will be "candid" when it disagrees with China, but will build a relationship based on co-operation
He also stressed the importance of economic ties between the two countries and emphasised China's growing role in international affairs.
The document represents a sort of stock-taking of ties between London and Beijing and sets out aspirations for the way in which Sino-UK ties should develop over the next four years.
Mr Wen has snubbed France during his European tour, reportedly because of a meeting between President Nicolas Sarkozy and the Dalai Lama late last year.
China reacted at the time by cancelling a scheduled summit with the EU.
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