Italy has arrested a man of Latvian origin suspected of planning to carry out a bomb attack on a kindergarten.

Italian police said on Thursday that Denis Illarionovs had been arrested on Monday. Police also found material used to assemble pipe bombs in the man’s apartment in the city of Viterbo, north of Rome.

The man had been planning an attack on a kindergarten, police said after receiving a tip-off from the FBI about his social media activity. He wrote on social media phrases, including one that read “it’s time to kill the children in the kindergarten.”

Illarionovs, 24, had also praised perpetrators of attacks in the United States, including Sayfullo Saipov, the suspect charged with killing eight people with a speeding truck in New York City last year.

A judge’s order said that Illarionovs had been considering an attack on a kindergarten. It also said that a police search of his apartment led to the discovery of material such as cylinders, solid explosive material, many small coins, metal plates, a digital scale, a digital thermometer, fuses, and an electrical resistor as well as an air rifle, two air pistols and weapons used in hand-to-hand combat such as brass knuckles.

Illarionovs has been charged with possession of explosive material. A judicial source said prosecutors could harden charges to terrorism offences and transfer the case to national anti-terrorism investigators in Rome.

Illarionovs has refused to answer questions regarding his activity on social media and possession of illegal explosives. He is reported to have gone through a troubled youth and lived by himself after his mother moved to Germany for work.