The arrests follow a wave of hoax alerts in recent weeks targeting politicians and media figures, including the home of opposition leader Jarosław Kaczyński and the flat of the mother of President Karol Nawrocki.
The latest arrest is a 29-year-old man from Otwock, near Warsaw, suspected of making two calls to the emergency services on 18 May claiming a bomb had been planted at a television station.
He has admitted the offence.
Police seized two mobile phones and a computer.
A Warsaw court has remanded him in custody for three months at the request of prosecutors.
Kierwiński said further arrests were planned.
"Zero tolerance for criminals," he wrote on X.
Following the incidents, the interior ministry convened an emergency meeting, and Prime Minister Donald Tusk held a briefing with ministers and security officials.
The ministry has established a dedicated task force including cybersecurity specialists and experts from the national cybersecurity agency NASK and the Internal Security Agency (ABW).
(ał)
Source: PAP