Two British extremists, who are banned from leaving the UK, have appeared in court in Budapest under armed guard after they were arrested in Hungary.

Trevor Brooks, also known as Abu Izzadeen, an infamous Islamist extremist who was jailed in 2008 for financing terrorism, was detained by officers on Saturday at Lokoshaza - a crossing point on the Hungarian border - while bound for Romania on a train.

He was stopped alongside fellow British extremist Simon Keeler, a Muslim convert, who was acquitted in July of planning to travel to Syria to join ISIS after being found in the back of a lorry at Dover.

Surrounded by heavily armed police officers, Abu Izzadeen prepares to enter the courthouse in Budapest

Keeler, 44, (centre) was acquitted in July of planning to travel to Syria to join ISIS after being found in the back of a lorry at Dover

Izzadeen, a London-born former Christian who converted to Islam on the eve of his 18th birthday, was stopped on Saturday by Hungarian police and reportedly presented officers with Islam's Holy Book as his form of identification.

Simon Keeler, 44, has also served time in prison for funding terrorism and was jailed for 15 months after admitting possession of false identity documents.

Both men appeared in Budapest Capital court under armed guard and could be extradited back to the UK.

Police said the pair were both were barred from leaving Britain without permission.

The two men were taken into custody by Hungarian police because they did not have legal documents entitling them to stay in the EU member state.

A spokesman said it was unclear what the men had been travelling, although it was possible they were on their way to Syria via Bulgaria and Turkey

British hate preacher Trevor Brooks, also known as Abu Izzadeen (left), who has been banned from leaving the UK after financing terrorism, has been held in Hungary - and gave officers the Koran for ID

Simon Keeler, also known as Sulayman, works behind the police as he prepares to enter the courtroom

Trevor Brooks (pictured), also known as Abu Izzadeen, an infamous Islamist extremist who was jailed in 2008 for financing terrorism, was stopped by officers on Saturday at Lokoshaza, Hungary

Keeler worked as a builder by day but in the evenings he used to help out on Islamist dawah stalls

It only emerged that they were subject to a European arrest warrant after they were detained, police spokeswoman Viktoria Csiszer-Kovacs told AFP. The men are due to appear in court in Budapest to over their possible extradition.

A spokesman said it was unclear what the men had been travelling, although it was possible they were on their way to Syria via Bulgaria and Turkey.

There was no suggestion that the men were implicated in Friday's deadly attacks in Paris.

Izzadeen was born to a Christian Jamaican family in London and worked as an electrician. He gained notoriety in 2006 after heckling Britain's then-home secretary John Reid live on television.

He also refused to condemn the 7/7 bombings in London and described then-prime minister Tony Blair and US President George W. Bush as the 'real terrorists' for invading Iraq and Afghanistan.

Abu Izzadeen (right) takes part in a demonstration alongside hate preacher Anjem Choudary in 2007

Izzadeen came to the attention of the media after his infamous tirade during a speech by John Reid

In 2008, Abu Izzadeen was jailed for four and a half years for terror-related offences