Twenty arrests included ex-lawmakers, according to Turkish sources, after raids that followed an announcement by France on Wednesday that nine Kurds were charged with terror offences, allegedly recruiting fighters for the PKK separatist group.

"We have very serious evidence that, in a very organised way, youngsters of Kurdish origin were recruited in western Europe, notably in Belgium," said Belgian federal prosecutors' spokeswoman Lieve Pellens.

"They were trained in camps in Europe -- notably in Belgium -- and in military camps, in Iraq and Greece," she said, adding that a number had joined fighters' ranks in Iraq and Turkey.

The 20 will go before a magistrate within the next 24 hours, facing potential charges of having "led" or been "a member of" a "terrorist organisation," the prosecutors' service underlined.

The Firat news agency, which is close to the PKK, reported that those detained included Remzi Kartal and Zubeyir Aydar, top figures coordinating PKK activities in Europe. Both are former Turkish parliament members.

In October, the US Treasury Department put Aydar on a list of "significant" foreign drug traffickers, along with two other PKK leaders, saying that they were using drug smuggling to help fund the PKK.

"I'd like to congratulate the Belgian authorities... We appreciate their determination and sense of responsibility," Turkish Foreign Minister Ahmet Davutoglu told reporters.

"This action by Belgium, following (similar operations in) Italy and France, carries a very strong message to groups and organisations providing financial resources for terrorist activities," he said.

However, a statement carried by Firat and issued by KCK, an umbrella Kurdish group led by the banned Kurdistan Workers' Party (PKK), urged "all Kurds living in Europe" to "come together in Brussels and mount actions of protest against this hostile attack."

Belgian public radio RTBF said some 300 officers took part in raids in Brussels, Antwerp and other Belgian cities, including at the offices of Kurdish international TV station Roj TV in Denderleeuw.

An AFP correspondent in Diyarbakir, largest city in the mainly Kurdish southeast of Turkey where Roj TV is widely watched, said that the channel's broadcast was cut on Thursday.

Seven of the nine French-based suspects were remanded following charges that included taking part in a terrorist enterprise, financing terrorist activities and violating gun laws.

Considered a terrorist group by the European Union and the United States, the PKK took up arms against Ankara in 1984, sparking a conflict that has claimed some 45,000 lives.

Ankara has long urged a clampdown on Kurdish militants in Europe, saying that they are financing the PKK -- listed as a terrorist group by Turkey and much of the international community -- through drug-trafficking, people smuggling and extortion.