PARIS — A suspect linked to the Nov. 13 Paris attackers was found with surveillance footage of a high-ranking Belgian nuclear official, the Belgian authorities acknowledged on Thursday, raising fears that the Islamic State is trying to obtain radioactive material for a terrorist attack.

The existence of the footage, which the police in Belgium seized on Nov. 30, was confirmed by Thierry Werts, a spokesman for Belgium’s federal prosecutor, after being reported in the Belgian daily newspaper La Dernière Heure.

The news set off an immediate outcry among Belgian lawmakers, who charged that they and the country had been misled about the extent of the potential threats to the country’s nuclear facilities, as well as about the ambitions of the terrorist network linked to the Islamic State that used Belgium to plot the Paris attacks, which killed 130 people.

The International Atomic Energy Agency and the State Department also confirmed on Thursday a report by Reuters that radioactive material had disappeared since November in Iraq, where the Islamic State controls broad areas of territory, adding to fears that the group may be able to acquire material for an attack with newly disconcerting dimensions.