Belgian police have increased security in Brussels after the arrest of 14 people in anti-terrorism raids.
The 14 alleged militants were detained earlier today in a police raid following the discovery of what officials said appeared to be plans for a prison breakout.
Security has been tightened in public places, such as the underground metro system, railway stations and the city's international airport, as well as at Christmas markets and in shopping districts.
A spokeswoman for Belgium's federal prosecutor's office told reporters that the arrests were made after police discovered a plan for a jail break involving 'weapons and explosives'.
The plan was to help free Nizar Trabelsi, who was sentenced in 2004 to 10 years in prison for planning, with other militants, an attack on a US military base in Belgium.
Once a professional footballer, Trabelsi later became a follower of al-Qaeda leader Osama bin Laden, after they met in Afghanistan.
Those arrested 'have an extreme vision of Islam and were preparing a prison breakout', spokeswoman Lieve Pellens said.
