German police have arrested two people they suspect are linked to the Islamist suicide bombers who killed 31 people in Brussels on Tuesday, the German newsmagazine Der Spiegel said in an unsourced report today.

It said one of the men, arrested on Wednesday near Frankfurt, received two mobile phone messages shortly before the bombings that included the name of Khalid El Bakraoui, the man Belgian police say blew himself in a Brussels metro station.

The German interior ministry declined immediate comment on Spiegel's report. The bombings at the metro station and in Brussels airport were the worst such attack in Belgian history.

The bombings at the metro station and in Brussels airport were the worst such attack in Belgian history

Der Spiegel said the messages included the word "fin," French for "end", and were received three minutes before the explosion at Brussels' Maelbeek metro station, near the European Union headquarters.

The attacks, claimed by the Islamic State insurgent group, raised concerns about cross-border security lapses that allowed European-born militants to evade arrest as they plotted attacks.

Germany's federal police chief said Islamic State appeared eager to carry out "spectacular" attacks as it was coming under increased military pressure in Iraq and Syria.

This means the risk of Brussels-style attacks in Germany and elsewhere in Europe is high, Holger Muench, president of the BKA federal police, told Bild newspaper in remarks to be published on Saturday. "More attacks cannot be ruled out," he said.