Police in Belgium arrested four teenagers on Sunday after they allegedly exchanged messages to plot a jihadi terror attack.

The four suspects — three minors in their "late teens" and an adult man aged 18 — were arrested when police raided home addresses in Brussels, Ninove, Charleroi and Liege.

A spokesperson for the federal prosecutor's office told the AFP news agency that the details of the alleged attack were deemed "worrying enough to intervene." 

"It's not that they were planning something tomorrow, but still imminent enough to intervene," spokesperson Eric Van Der Sypt said. 

Police raided the suspects' homes and retrieved mobile phones and laptops for further analysis. They did not recover any weapons or explosives.

Terror threat level 3

Sunday's arrests were the result of a police operation looking into people deemed potentially violent and with links to Islamic extremism.

Belgian Justice Minister Paul Van Tigchelt told reporters that it was not the first time that authorities identified young people who had been radicalized quickly.

Local authorities have remained highly vigilant since the 2016 attacks by suicide bombers that killed 32 people in blasts at Brussels airport and the city's metro system.

The terrorist alert level in Belgium is currently at level 3, which means that there is a serious risk of attack, and that threats are possible and probable. The highest level, 4, means that an attack is imminent.

zc/nm (AFP, EFE)