Image caption Court drawings left the faces of MI5 agents (left) blank - Naseer is on the right

MI5 agents, wearing wigs and make-up to hide their identities, have told a US jury how they tracked a man accused of a transatlantic bomb plot.

Abid Naseer, who was extradited from the UK in 2013, is accused of plotting bomb attacks in Manchester and New York as part of an al Qaeda conspiracy.

He has pleaded not guilty and denied he was involved in any violent extremism.

A judge has made several rulings to protect the spies' identities, including modified court sketches.

Judge Raymond Dearie had previously approved the wigs and "light" make-up to protect the identifies of the officers and ordered courtroom sketch artists to further generalise their appearance over media organisation's objections.

Mr Naseer faces life in prison if convicted of the charges against him - providing and conspiring to provide material support to al Qaeda and conspiring to use a destructive device.

Prosecutors have called the testimony of the MI5 agents essential, saying they tracked Mr Naseer in 2009 and were the only witnesses to his alleged preparation to attack a Manchester shopping centre.

Inside the courtroom - Nick Bryant, BBC News

In a courthouse in Brooklyn, there was the sort of make-up and hair ordinarily associated with theatrical productions on Broadway.

The first MI5 agent who took the stand, known as Officer 1661, wore glasses, a jet-black wig and also a beard - though it was hard to tell whether the facial hair was real or artificial. Speaking in a northern English accent, he described how he had conducted surveillance in Liverpool and Manchester on the defendant Abid Naseer.

Others agents who took the stand included a female agent, Officer 1488, who wore glasses and a shoulder length brown wig, and a third agent, who looked to be of an Asian background, also wore glasses and a black wig.

Throughout the proceedings, they were watched by a representative of the British government, who himself wore a wig and glasses. He also scrutinised the drawings of court artists, who had been instructed by the judge to depict blank faces and generic hair.

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The agents followed him as he visited a shopping centre in Manchester, allegedly the target of the plot, a mosque and other locations.

He was previously arrested in the UK on suspicion of plotting an attack.

No explosives were found but he and others were ordered to leave the country. Mr Naseer avoided deportation to Pakistan.

US prosecutors have argued Mr Naseer was the leader of an al-Qaeda cell in Manchester and involved in planning bomb plots in multiple countries, including an alleged plan to bomb the New York city subway.

Mr Naseer is representing himself and has said he went online and used email to find a wife, not contact an al-Qaeda handler, as prosecutors have alleged.

But one officer told the court he had never seen Mr Naseer in the company of a woman.

Image caption Mr Naseer (seen here in 2010) was previously arrested in the UK over a bomb plot in Manchester

Image copyright Other

On Tuesday, Mr Naseer had the opportunity to cross-examine the intelligence officer who had tracked him in the UK.

"Did these movements cause any alarm or suspicion?" he asked. "No," the man, known as Officer 1661, replied.

Evidence from another MI5 spy was recorded last month and played in court in Brooklyn last week.

The officer said he followed Abid Naseer onto a coach and observed him watching a video of the 9/11 attacks on his mobile phone.

UK officials arrested him at the request of US prosecutors several years ago. He was eventually deported after losing an appeal at the European Court of Human Rights.