Chinese President Xi Jinping concluded his visit to Britain on Friday with a call for Britain to remain in the European Union and a trip to see the English Premier League leaders Manchester City.

After three days of banquets, processions and trade talks, Xi posed for a "selfie" picture with Sergio Aguero, City's Argentinian star striker, and British Prime Minister David Cameron at the football club.

The four-day trip focused on strengthening relations between London and Beijing, particularly trade ties, and Cameron's office announced deals worth almost 40 billion pounds ($61.6 billion, 54.4 billion euros).

During his official talks with Cameron on Thursday, the Chinese foreign ministry reported Xi as saying he hoped Britain would remain in the European Union -- a hot-button political topic for the British leader.

"China hopes Britain will be an important member country of the European Union to be a more positive and constructive element to deepen the development of Sino-European relations," the ministry paraphrased Xi as saying in an official statement.

Contacted by AFP, Downing Street declined to comment.

Cameron has promised to hold a referendum on Britain's EU membership by 2017 under pressure from eurosceptics within his own Conservative Party and the anti-EU UK Independence Party.

Xi's pomp-filled visit proved controversial.

Some campaigners felt Britain should have pushed Xi more on human rights issues, while others were angry at the closure of British steelworks, partly due to cheaper Chinese steel.

Cameron accompanied Xi on his tour of Manchester on Friday as the UK government tries to promote investment in the post-industrial cities of northern England.

Xi is reportedly a fan of Manchester United, who host their local rivals Manchester City in the Premier League on Sunday.

But he visited City's academy, a state-of-the-art training facility that includes a 7,000-capacity stadium and 16 football pitches able to cater for more than 450 players.

He watched a training match and met players who helped build the city's footballing legacy, including former United captain Gary Neville and ex-City star Patrick Vieira.

Xi and Cameron also toured the National Football Museum, seeing a football used in the first-ever World Cup final in 1930.

Xi inducted former City player Sun Jihai into the museum's Hall of Fame, in recognition of his role enhancing the popularity of English football in China. Sun was the first Chinese player to score in the Premier League.

- 'Strongest partner in West' -

The British government is keen to promote its "Northern Powerhouse" project, in which councils in the post-industrial north of England are being given more powers in an attempt to stimulate their economies.

Xi had lunch with around 200 business and civic leaders at Manchester Town Hall, where hundreds of organised British-based Chinese greeted his arrival, waving Chinese flags handed out from cardboard boxes.

A small number of protesters were grouped with a banner demanding "Justice For Human Rights".

"We see ourselves as China's strongest partner in the West," Britain's finance minister George Osborne said during Xi's tour of the city.

"A partnership is a relationship where we do things together, like build nuclear power stations, invest in modern science, regenerate cities like Manchester.

"A partnership is also where you can have frank discussions about issues like the future of steelmaking or cyber security or, indeed, human rights."

A clutch of business contracts have been announced during Xi's four-day visit, as well as the launch of the first yuan-denominated bond in London as China seeks to internationalise its currency.

As part of a raft of partnership deals, Hainan Airlines announced its first direct flights from Manchester Airport to China, before Xi flew home from Britain's third-biggest air hub.

Meanwhile British police arrested a survivor of the Tiananmen Square crackdown and raided his home after he stepped out in front of Xi's motorcade, police and campaigners said Friday.

London police said Shao Jiang was arrested and later released on bail on suspicion of "conspiracy to commit threatening behaviour".