Prosecutor Piotr Antoni Skiba, a spokesman for the Warsaw District Prosecutor’s Office, said that the Warsaw-Mokotów District Court granted a prosecution request for the detention of the suspect, identified only as Krzysztof N. under Polish privacy laws.
Skiba said the request took into account the ongoing nature of the investigation, the severity of the potential punishment and concerns that the suspect could interfere with the proceedings.
He added that the suspect himself had "indicated a threat of a serious crime against life and health."
The prosecution service said it would provide further details on Thursday.
Poland's interior ministry said on Sunday that police had received information about a possible attack targeting Tusk and Deputy Prime Minister Władysław Kosiniak-Kamysz.
A meeting of police, State Protection Service (SOP) and Internal Security Agency (ABW) commanders was subsequently held. The 66-year-old man was detained later that day.
The suspect was brought before prosecutors in Warsaw on Tuesday and charged with nine offences. The most serious allegation involves "planning the violent overthrow of state authorities," an offence punishable by two to 15 years in prison.
The other charges involve recordings posted online that prosecutors said promoted "the violent seizure of power" in Poland, and "the use of violence and efforts to bring about political change."
They also concern "the promotion of Russia’s war of aggression," including in Ukraine, and "calls for crimes based on nationality, ethnicity, race and political affiliation."
During a search of the suspect's home, authorities found more than a dozen improvised explosive devices.
Skiba said on Tuesday that an initial assessment indicated that the devices were improvised explosive materials resembling fragmentation grenades. He said the findings would have to be verified through a forensic experiment.
Authorities also found objects resembling weapons that were initially classified as alarm weapons or pneumatic weapons, Skiba said.
Investigators also seized a list of people who had been in contact with the suspect and computer equipment, which has been submitted for analysis.
According to Skiba, the suspect claimed that a group with radical views had been formed to promote the idea of taking power in Poland by force. He said the suspect claimed the group was to have three units, with a fourth being formed.
Skiba said there was "currently no indication" that the group had been inspired or directed by foreign intelligence services, although that possibility was still being investigated.
"At first glance, it might seem that we are dealing with some kind of gang of incompetents, but given the facts, the case appears quite serious," Skiba said.
He added that a separate investigation had been conducted in recent weeks by prosecutors in the east-central city of Kielce and was transferred on Tuesday to the Warsaw prosecution service.
That investigation concerned various online posts promoting "behaviour that violated the law," according to Skiba.
(gs)
Source: IAR/PAP