Britons fighting in Syria 'are being trained by al-Qaeda to make car bombs and suicide vests to launch attacks when they return to the UK' Defector claims foreign fighters are being brainwashed by fanatics Are urged to go home, set up terror cells and carry out atrocities like 9/11 One American claimed his dream was to 'blow up the White House' Security services concerned many who return could carry out attacks Feared 500 Britons are fighting Bashar al-Assad's regime British people fighting against the Syrian regime are being trained as 'jihadists' and urged to launch attacks in the UK when they return. Fighters who have travelled to the country to join the battle against Bashar al-Assad's government are being brainwashed into becoming terrorists before they are encouraged to return home and set up terror cells, an al-Qaeda defector revealed. Extremists are teaching them how to construct and detonate devices like car bombs and suicide vests so they are prepared to return to Britain and carry out atrocities similar to 9/11 or the London bombings. Security fears: Foreign fighters joining the attempt to overthrow the al-Assad regime are being brainwashed by fanatics so they can carry out atrocities similar to 9/11 and the London bombings (file picture) It is feared 500 Britons are among the of thousands of foreign fighters in the war-torn country, and security services are concerned that many could return to carry out attacks on home soil. MI5 is said to have increased the number of resources to tackling the danger in the past six months. The defector from the Islamic State of Iraq and al-Sham (ISIS) told The Daily Telegraph that some of those who want to overthrow the Assad regime are being turned by fanatics. Known as Murad, the former extremist said foreign fighters have 'often talked about terrorist attacks' suggesting they were 'proud of 9/11 and the London bombings'. Prepared: The fighters from abroad are being taught how to construct explosives such as car bombs and suicide vests (file picture) 'The British, French and American mujahideen (holy warriors) in the room started talking about places that they wanted to bomb or explode themselves in Europe and the United States,' he said. The American dreamed of blowing up the White House. A stream of young men have left everything they have at home in Britain to fight in the violent revolution, while Shirz Maher, a senior research fellow at King's College London, has estimated 50 may have already returned. Ifthekar Jaman, 23, travelled more than 2,000 miles to fight in a bid to overthrow the Assad regime and developed into a '5-star jihad'. He was shot and killed in December, a month after declaring he was ready to die as a martyr, vowing: "I don't plan to come back. Life is for the hereafter... it's an eternal paradise so the sacrifice is small. British involvement: Mohammed el-Araj, from West London, (left) was killed during an ambush on Assad forces earlier this year. Another Briton, Abu Hujama al-Britani, right, was also killed. Centre is a former Dutch soldier who trained them Ifthekar Jaman, 23, is one of the Britons who travelled more than 2,000 miles to fight in the revolution and boasted he was a '5-star jihad Abdel-Majed Abdel Bary, 23, is another to join militant groups in the Middle Eastern country. He walked out of his family's £1million home several months ago telling them he was 'leaving everything for the sake of Allah'. Friends said Bary - an aspiring rapper on the 'grime' music scene - grew increasingly radical and violent after mixing with thugs linked to hate preacher Anjem Choudary. Last Friday, two 21-year-old men from Birmingham were charged with travelling to Syria to carry out terrorist acts. Yusuf Sawar and Mohammed Ahmed, from Handsworth, Birmingham, were arrested at Heathrow after arriving on a flight from Turkey. It also emerged last week that two French schoolboys have travelled to Syria to become Al Qaeda fighters. The youngsters were reported missing after they failed to turn up at school on January 6, instead using a credit card to book flights to the Middle East. Manuel Valls, France's interior minister, said citizens returning from Syria as extremists was the 'biggest threat the country faces in the coming years', estimating that 700 French nationals have been involved in the conflict. Recruit: Abdel Majed Abdel Bary, 23, is another Briton who has joined militant groups in the war-torn Middle Eastern country Radicalised: Many of Britons who have travelled to the Middle-Eastern country are said to have been influenced by the radical teachings of Anjem Choudary