A man arrested in Canada on terrorism charges has been linked to a major anti-terror operation in Sussex.

Mohammed Momin Khawaja, 24, from Ottawa, was arrested after armed officers with battering rams raided his home.

His arrest came a day after Ahmad Khan, 18, Omar Khyam, 22, and Shujah Khyam, were arrested at an address in Langley Drive, Crawley during anti-terrorism raids.

Khawaja worked at the Foreign Affairs Department. Officers said he had been detained for allegedly "enhancing the ability of a terrorist group to facilitate or carry out a terrorist activity".

His brother said police had seized an innocent man but the Mounties said in a statement there were links to the terrorism operation which led to the arrests of eight suspects from across the South-East of England.

Mounties said Khawaja was part of an alleged conspiracy hatched in London and Ottawa which took shape some time after November 10.

Officers in Crawley yesterday stepped up operations, closing off an area of scrubland next to the town's police station.

The land, on the edge of Crawley College car park in Northgate Avenue, was cordoned and searched but officers would not reveal if it was connected to the arrests.

Their search focussed on a Seeboard gas substation on the edge of the car park.

A team of officers dressed in chemical suits, gloves and surgical masks examined the site and took photographs.

Crawley police said searches were likely to continue for several days.

Investigations are being carried out at Gatwick Holiday Inn in Horley where another suspect was arrested during Tuesday's raids.

Officers sealed off two rooms on the fourth floor, which have been placed off limits.

A police guard was placed outside the doors as items from inside the rooms were taken away for examination.

A relative of three suspects arrested in Crawley yesterday protested their innocence and insisted the family was visited by MI5 officers and asked to leave the country before the raid.

Sajjad Ahmed, the uncle of two of the suspects, produced a mobile phone with what he claimed was the number of his MI5 contact but when he called the number he was redirected to an answering machine.

Mr Ahmed told Channel 4 News Omar and Shujah Khyam had recently been visited by a mysterious Mr Gould, who claimed to be from the security service.

However, the programme reported a security source had denied any officer from MI5 had met Mr Ahmed or any of his family.

Mr Ahmed was adamant MI5 met him three times to explain while his nephews were not a threat themselves, they had been spotted with people who were.

He insists his nephews are innocent.

However, he criticised teaching at local mosques and said he had tried to encourage his son to read books instead.

Jaleel Meedin, secretary of the Crawley Mosque, denied there was anything improper in their teaching.

He said: "The mosque is a place of worship of Islamic studies and where we teach the Koran. There is nothing controversial in this and anyone who wishes to partake can come and see for themselves.

"We have good relations with the local police and other agencies.

We realise they have a difficult job to do and we co-operate with them.

"We hope in time everything will settle down and we will be able to carry on as before, continuing our good relations with the Crawley community."

The Muslim Council of Britain, the country's largest Islamic organisation, has written to 1,000 mosques urging them to maintain the "utmost vigilance" in the war against terror.

The increased police activity and the allegations of terrorism has made many people in Crawley anxious.

Crowds watched as parts of the town centre were sealed off to make way for officers to search for evidence.

Ronnie Trineck, who was visiting friends at the Gales Drive, off Northgate Avenue, complained police had not given any explanation.

He said: "I think they have found something in an alleyway. There are police all over the place. I thought it was a bomb but police have told no one.

"On Tuesday they said it was police training but they're still here."

Ted McDonald, who lives behind the cordoned-off scrubland in Friars Rookery, said: "I looked over our back gate and saw 14 police officers walking about in chemical suits.

"It has been like this since 4pm on Tuesday. It's frustrating because they are not telling us what is going on. We are left in the dark.

"We see a lot of activity at the police station because we are overlooking it. You're always aware of something going on because you hear the sirens.

"We accept that but, all of a sudden, there are all these people wearing protective clothing and when we ask no one divulges exactly what's what."

An internet cafe in Langley Green was also targeted in Tuesday raids. Jafar Nazir, 34, who runs PC UK, said officers told him two of the suspects had used computers at the cafe and they needed to check the records.

He said: "They waited for two hours outside the shop until we arrived, which was considerate."

Police took five computers and up to nine laptops. Mr Nazir said he did not know the names of the suspects and they had been in only "a few times" before.