BRUSSELS (Reuters) - Belgium charged a man with planning to commit murder in a terrorist attack and released his brother after a series of house searches on Friday evening, federal prosecutors said.

For the time being, there was no connection with the attacks at Brussels airport and the metro on March 22, in which 32 people were killed, the prosecution office said on Saturday.

Nourredine H., was detained with his brother Hamza H., on suspicion of planning a terrorist attack somewhere in Belgium.

A judge on Saturday charged Nourredine with attempting to commit a terrorist murder and participation in the activities of a terrorist organisation, and extended his custody.

His brother was released without charge.

The federal prosecution office had earlier said it appeared from its initial investigation that there were plans to carry out an attack somewhere in the country.

Public broadcaster RTBF said that Nourredine had previously helped others travel to fight in Syria and had recently travelled widely across Europe, making a number of contacts in France. It added he was looking for weapons, which had prompted Belgian investigators to act.

Police carried out seven house searches in the region of Mons and a further house search in Liege on Friday evening. No weapons or explosives were found.

Brussels, home to European Union institutions and the headquarters of NATO, and Belgium in general are on a security alert level of three out of a maximum of four, a "serious" status with a "possible and probable" threat.

(Reporting By Philip Blenkinsop; Editing by Angus MacSwan and Alexander Smith)