British Prime Minister David Cameron said Tuesday he had ordered an investigation into the Muslim Brotherhood over concerns that the group, declared a terrorist organisation by Egypt and Saudi Arabia, is linked to violent extremism.
Key leaders of the group have been based in London since the toppling of the Islamist Egyptian president Mohamed Morsi last year and a crackdown that has seen hundreds killed and thousands arrested.
The new Egyptian government welcomed the British inquiry, which will reportedly see intelligence agencies assessing claims that the Brotherhood was linked to a suicide bus bombing in Sinai that killed three South Korean tourists in February and to other attacks.
Cameron said the inquiry was partly due to concerns over extremism following the brutal murder of British soldier Lee Rigby in a London street by two Islamist converts last year.
Britain must "fully understand what this organisation is, what it stands for, what its links are, what its beliefs are in terms of both extremism and violent extremism, what its connections are with other groups, what its presence is here," Cameron told a joint press conference with visiting Italian premier Matteo Renzi.
The inquiry by John Jenkins, Britain's ambassador to Saudi Arabia, would paint a "complete picture" of the organisation, Cameron added.
Egypt's foreign ministry spokesman Badr Abdelatty welcomed the investigation, saying in a statement that he "hoped the matter will be addressed with the necessary seriousness and attention".
The Brotherhood's leader Gomaa Amin, who came to London before the coup for medical treatment, and Ibrahim Munir, a member of the group's guidance council, are both currently based in the British capital.
The group's press office is also based in the city.
They gathered in a flat above an Islamic charity office in the drab northwest London suburb of Cricklewood, according to The Times newspaper.
In a statement received by AFP in Cairo, the Muslim Brotherhood said its members in Britain "fully respect the institutions and laws of the country in which they live.
"The Muslim Brotherhood calls on the Western governments and states to be careful as the military junta is trying to pressure (them) in order to distort the reality about the Brotherhood and what is happening in Egypt," it added.
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- 'Possible but unlikely' ban -
The Brotherhood was founded in Egypt in 1928 and despite years of repression it remains the largest Islamic movement in the Middle East, having particularly returned to prominence during the Arab Spring uprisings.
Morsi, who belongs to the Brotherhood, became Egypt's first elected civilian president following the toppling of Hosni Mubarak in 2011, but he was ousted by the army last July after a single year in power. He now faces three separate trials.
Egypt's military-installed government in December declared the Brotherhood a "terrorist organisation". Saudi Arabia followed suit last month.
In Egypt more than 1,400 people have been killed in street clashes and thousands imprisoned, including the Brotherhood's top leadership.
A judge triggered a global outcry last month for sentencing 529 Morsi supporters to death for murder and attempted murder of policemen in riots.
Other senior Brotherhood members are in Doha and Egypt is requesting their extradition from Qatar.
The Brotherhood says it has eschewed violence for decades.
The Times reported that it was "possible but unlikely" the probe could lead to a ban on the Muslim Brotherhood in Britain.
Britain's domestic spy agency MI5 and foreign intelligence agency MI6 had both been tasked with gathering information on the group, the daily said.
Cameron's Downing Street office said in a statement to AFP that the Brotherhood had "risen in prominence in recent years but our understanding of the organisation -- its philosophy and values -- has not kept pace with this".
London has long played host to political exiles of all stripes from around the world.