Belgian prosecutors say they have arrested two people suspected of plotting militant attacks in Brussels on New Year's Eve.

The arrests were part of an anti-terrorist operation across the city and the neighbouring Brabant region as well as in the Liege area on Sunday and Monday.

Six people were initially questioned after house searches but four of them were released, prosecutors said.

Police found military clothing and Islamic State propaganda and computer material which investigators are examining, but no weapons or explosives.

The searches were not linked to the November Paris attacks in which 130 people were killed. 

Prosecutors said in a statement: "Our investigation revealed serious threats of an attack on symbolic places in Brussels during the celebrations for New Year's Eve."

The two held were accused of terror threats and participation in terrorist activity, with one of them allegedly "in the role of a leader and involved in recruiting".

It come after schools, universities and the Metro were shut down in Brussels for several days last month after authorities raised the alert over a "serious and imminent" terror threat.

Belgium, and Brussels in particular, have been at the centre of investigations into the Paris attacks after it emerged that two of the suicide bombers who attacked the French capital had lived in the country.

Belgian authorities have arrested a number of people on suspicion of involvement in those attacks, which have been claimed by Islamic State.

Two of the Paris suicide bombers, Brahim Abdeslam and Bilal Hadfi, had been living in Belgium.

Brahim's brother, Salah Abdeslam, a key suspect in the attacks on November 13, had fled to Belgium afterwards and remains on the run.

The car he was in was said to have been stopped three times by French police unaware that one of the passengers was Europe's most wanted fugitive.

Belgian national Abdelhamid Abaaoud was suspected of being the ringleader of the Paris attacks. He was later killed in a siege of a flat in a Paris suburb.