Two teenage boys, aged 16 and 17, have been arrested in Belgium and are accused of pledging allegiance to the ISIS group and plotting to attack police officers with knives, prosecutors said.
The two were arrested late Saturday in the eastern town of Eupen, near the border with Germany, and are being held in a detention facility for minors.
Belgium state broadcaster RTBF said they had recorded videos of themselves swearing loyalty to IS.
The IS group has claimed responsibility for the shooting attack by an Austrian-Macedonian man in Vienna on Monday which left four people dead.
Belgium has already been targeted by the ISIS , including in March 2016 when suicide attackers killed 32 people and wounded 340 others in blasts at Brussels airport and in a metro station in the capital.
In May 2018, a radicalised man murdered two police officers and a student in an attack claimed by the ISIS group.