Media playback is unsupported on your device Media caption Donald Trump has accused China of trade 'rape'

Republican presidential front-runner Donald Trump has accused China of "raping" the US, in renewed criticism of China's trade policy.

He told a rally in Indiana that China was responsible for "the greatest theft in the history of the world".

Mr Trump, a billionaire businessman, has long accused China of manipulating its currency to make its exports more competitive globally.

This, he says, has badly damaged US businesses and workers.

"We can't continue to allow China to rape our country, and that's what we're doing," he told the campaign rally on Sunday.

"We're going to turn it around, and we have the cards, don't forget it," he added. "We have a lot of power with China."

China's complex relationship with Trump

Trump favours high tariffs on China exports

Mr Trump, in his campaign manifesto, pledges to "cut a better deal with China that helps American businesses and workers compete".

He sets out four goals that include immediately declaring China "a currency manipulator" and putting "an end to China's illegal export subsidies and lax labour and environmental standards".

Figures from the US government show the annual trade deficit with China was at an all-time high of $365.7bn (£250.1bn) last year.

There was no immediate response from Beijing to Mr Trump's comments, but he is seen by many in China as an inspiration rather than an antagonist, says the BBC's Vincent Ni.

What's behind Trump's comments? Bill Wilson, BBC News business reporter

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Donald Trump has repeatedly accused China of manipulating its currency to make its exports more competitive, with what he says are damaging consequences for the US economy.

Rather than floating freely against the dollar, the Chinese authorities ensure the yuan maintains a closely fixed relationship with the US currency, and that it only trades in a narrow band either side of a fixed point selected by China.

Critics, including Mr Trump, claim China is keeping its currency at an unnaturally low level to boost its exports to the US, which also damages the prospects of US firms selling their goods to China. That, they say, has created in a huge trade imbalance.

Latest figures from Washington for US-China goods trade in January and February show the relationship does appear to be skewed. In those months the US exported $16.3bn in goods to China, but imported $73.3bn, leaving a massive goods trade imbalance of $57bn.

Last week, the US Treasury placed China (and others) on a currency watchlist, after pressure on the US government to be more robust in combating any currency manipulation by trading partners.

The Treasury stated that none of its large trading partners had engaged in currency manipulation in the past year, but indicated it was concerned about growing imbalances with some of those partners, including China.

Protesters

This is the first time Mr Trump has used the word "rape" in the context of China and trade, but his campaign for the Republican Party's presidential nomination has been punctuated by inflammatory comments.

He was confronted by hundreds of protesters in California on Friday before giving a speech to the state's Republican convention. Mr Trump was forced to enter the building by the back entrance.

Protesters were angry at his views on immigration: he has advocated building a border wall with Mexico, and has also referred to Mexicans as "rapists" and criminals responsible for bringing illegal drugs into the US.

Anti-Trump protesters were also out in force during the annual May Day rallies in California.

Media playback is unsupported on your device Media caption There have been widespread protests in California against Donald Trump's candidacy

The Trump campaign had to cancel several rallies in March after hundreds of protesters threatened to disrupt events in Chicago and St Louis.

Mr Trump has called himself the Republican "presumptive nominee" after a string of primary wins.

In terms of delegate support, the property tycoon is far ahead of his nearest rivals, Texas Senator Ted Cruz and John Kasich, the governor of Ohio.

On the other side of the race, Hillary Clinton is expected to beat Bernie Sanders to the Democratic nomination and fight for the presidency in November's general election.