Stations on Brussels' metro have reopened after the system was shut down following fears of a Paris-style attack.

Police and security services will be deployed to guard the network as it is gradually opened, and troops will continue to patrol the streets.

City schools which closed following police raids at the weekend are also expected to open, but Brussels' maximum security alert will be extended until next Monday.

Following the raids prosecutors charged a fourth person with terrorist offences linked to the Paris attacks, but released 15 others.

Some 300 additional police officers and 200 soldiers will be deployed as the hunt continues for suspects involved in the Islamist militant attacks which killed 130 people.

Belgium's state prosecutor announced that an international arrest warrant had been issued for Mohamed Abrini, who was seen with prime suspect Salah Abdeslam two days before the attacks.

Abdeslam is suspected of playing at least a logistical role in the co-ordinated shootings and suicide bombings on November 13th, but so far has evaded police capture.

Meanwhile, police have said the man thought to have been the ringleader of the attacks returned to the Bataclan concert hall while police were still there.

City prosecutor Francois Molins said phone records showed that Abdelhamid Abaaoud went back to the theatre where 89 people were shot dead, as an operation to free hostages was ongoing.

"The geolocalisation of Abdelhamid Abaaoud's alleged phone between 22.28pm and 0.28am confirms a presence in the 12th, 11th, and 10th districts, and notably near the Bataclan concert hall," he said.

"This allows us to think that Abaaoud returns to the crime scenes following the attacks on terraces of the cafes and restaurants of the 10th and 11th districts while (special police) were still taking action at the Bataclan".

Abaaoud was also thought to have been preparing with an accomplice for a suicide bombing mission at La Defense business district in Paris on November 18th or 19th, Mr Molins said.

Instead, the jihadist was killed during a police raid on the northern Paris apartment where he was staying in the early hours of November 18th.

Meanwhile, the Minister for Foreign Affairs here will face questions on the international terror threat in the wake of the Paris attacks today.

Charlie Flanagan is to address the Oireachtas Foreign Affairs committee on a number of issues.