"We don't know where the suicide attack was to take place," federal prosecutor Johan Delmulle told reporters.

"It could have been an operation in Pakistan or Afghanistan, but it can't be ruled out that Belgium or Europe could have been the target."

The raids came as European leaders gathered in the Belgian capital for a two-day summit.

The suspect in question had "received the green light to carry out an operation from which he was not expected to come back," and "had said goodbye to his loved ones, because he wanted to enter paradise with a clear conscience," Delmulle cited investigators as saying.

He had recorded a farewell video and assured that his relatives were taken somewhere safe, according to the investigators.

"This information, linked to the fact that a European summit is getting underway at this moment in Brussels, left us no choice but to take action today," he said.

Judicial police chief Glen Audenaert said 242 police officers carried out 16 raids in Brussels and one in the eastern city of Liege.

The 14 arrested suspects, men and women, were set to appear before anti-terrorism judges later Thursday.

The enquiry described as "the biggest" anti-terrorism operation in Belgium is linked to a Belgian Islamist group involved in training as well as fighting on the Pakistan-Afghan border, in liaison with "important figures" in Al-Qaeda, according to the federal prosecutor's office.

The year-old investigation "probably prevented plans for an attack from being carried out in Brussels," last year, it added.

Four Belgian nationals, along with others, had been in Pakistan and Afghanistan since late 2007, according to the authorities.

Two of the men returned to Belgium some months ago and were placed under surveillance.

A third, the suicide attack suspect, returned only last week.

All three were among those arrested Thursday. The other detainees were suspected of offering "logistic and material support" to the mission.

The investigation got underway last year, prompted by information about a plan to spring Tunisian Nizar Trabelsi from jail with the help of explosives and firearms.

Trabelsi was serving a 10-year term for plotting, in 2001, an Al-Qaeda-backed attack on a Belgian military base where US soldiers were based.

(AFP/Expatica)