The investigation into last week's bombings in Belgium extended farther across Europe after Italian police arrested a new suspect thought to have provided false documents to the Isis (Islamic State) militants behind recent attacks in Brussels and in Paris.
The Italian arrest adds to an emerging picture of the network that staged some of the worst attacks on European soil since World War II, another striking indication of the reach of Isis beyond its strongholds in Iraq and Syria.
Fears remained heightened across the continent nearly a week after suicide bombers killed at least 31 people at Brussels Airport and, an hour later, in a crowded subway car. Dutch anti-terrorism police arrested a 32-year-old man in Rotterdam on suspicion of preparing an attack on France and also detained three other people, national prosecutors say. "French authorities requested the arrest of the French citizen, who had been identified in a terrorism investigation," prosecutors said. He was suspected of "involvement in preparing a terrorist attack".
In St Peter's Square in Vatican City, worshippers were subject to tight security as they flocked to hear Pope Francis deliver his Easter address. Speaking to the crowed, the Pope called terrorism a "blind and brutal form of violence".
In central Brussels, widespread anxiety was visible as riot police with shields and white helmets fanned around a memorial site for victims. Police briefly fired water cannons after several hundred men dressed in black, apparently football fans, advanced into the area. The fans waved a giant banner against Isis and, according to some media reports, shouted nationalist slogans.
Government officials urged organisers to postpone a solidarity rally, saying that police could not provide adequate security.
Belgian authorities expanded their hunt for new clues. They conducted 13 searches in Brussels and other areas, the federal prosecutor's office said. Four people detained in those searches remain in custody.
Prosecutors also charged another suspect linked to the attacks. The man, identified by authorities only as Abderrahmane A., has been in custody since Saturday and faces charges of belonging to a terrorist organisation. Belgian police did not provide additional details.
The man who Italian authorities captured on Sunday was an Algerian suspected of providing several Isis supporters with false identification documents, allowing them to evade authorities while plotting attacks in Belgium and France.
According to the Italian news agency ANSA, 40-year-old Djamal Eddine Ouali had been the subject of a Belgian arrest warrant since January. ANSA said he was suspected to have given falsified papers to Salah Abdeslam, a suspected member of the cell that carried out the November Paris attacks and who is now in Belgian custody. Ouali is also believed to have furnished documents to Najim Laachraoui, suspected to have been one of the suicide bombers at Brussels Airport, and to another man killed by Belgian authorities in a raid this month before the attacks.
The latest person to be charged may be Abderrahmane Ameroud, whom Belgian media has reported as linked to the attacks. Ameroud was sentenced by a French court to seven years in prison for involvement in a plot to assassinate Ahmed Shah Massoud, a legendary Afghan guerrilla leader. Massoud was killed in 2001 shortly before the 9/11 attacks.