Belgian government said on Monday that the highest security threat level will remain until Wednesday in Brussels as the key suspect of deadly Paris attack is reportedly in the country.
Belgium police extended the operations to hunt down Belgian-born Salah Abdeslam who is believed to have entered the country after carrying out the bloody Paris attack with gunmen and suicide bombers on November 13, killing more than 130 people.
Belgian prosecutors announced on Monday that they have arrested 21 people in the raids since Sunday. However the detainees have not included the fugitive Abdeslam.
The authorities charged on Mohammed Amri, 27, and Hamza Attou, 20 on Monday for helping Abdeslam to escape to Brussels after the attacks.
According to Attou, Abdeslam may be equipped with a suicide belt and blew up himself during the attacks.
Prime Minister Charles Michel warned Monday that the threat "remains serious and imminent," adding that Brussels will keep on the highest level four alert as the rest of the country remains on a level three alert.
A source close to investigation said on Tuesday that Paris police were analyzing a suicide belt having "the same configuration" with the other belts used in the Paris attacks.
Following the growing fear over "increased terrorist threats," US government issued a worldwide travel alert warning American citizens.
A State Department travel advisory said on Tuesday that "Current information suggests that ISIL [DAESH] , Al Qaeda, Boko Haram and other terrorist groups continue to plan terrorist attacks in multiple regions."
The warning came as French President Francois Hollande is preparing series of meeting to convince world leaders to take common action against DAESH terrorist organisation.
Hollande will meet with the US President Barack Obama on Tuesday and he will hold talks with German Chancellor Angela Merkel on Wednesday, Russian President Vladimir Putin on Thursday and Chinese President Xi Jinping on Sunday.
The UN Security Council agreed on Friday to take "all necessary measures" to fight the group.
Belgium is also seeking to cooperate with Morocco to extend its intelligence-sharing to keep itself safe from the Paris-style attack.
A Belgian official said that King Philippe stood ready to help the government with the anti-terror effort, adding that contacts at the highest level would certainly help.