Tusk said there was no such evidence in the case of a separate fire at a production and storage facility in the eastern city of Lublin, but added that deliberate arson could not be ruled out given the nature of the company's production.
Tusk spoke before a Cabinet meeting about fires in recent days at two industrial facilities: a plant operated by defence contractor WB Electronics in Skarżysko-Kamienna that produces unmanned systems and a production and storage hall operated in Lublin by JFG Composites, which makes components used in aircraft construction.
"As for the fires at the two plants ... in the case of Skarżysko-Kamienna, there is no doubt that it was deliberate arson, an act of sabotage," Tusk said.
"In the case of Lublin, we do not have such evidence, but given the nature of the production, it cannot be ruled out that deliberate arson also occurred there," he said.
Tusk said the coming weeks and months would be critical not only for the war between Russia and Ukraine but also a major challenge for countries across the region because of what he described as Russian plans to increase tensions and destabilise the area.
Tusk says Russia uses cryptocurrency to fund sabotage
Tusk also linked the fires to a planned vote on Friday in Poland's parliament on President Karol Nawrocki's veto of legislation regulating the cryptocurrency market.
He urged opposition lawmakers and Nawrocki to change their position on the bill, saying its adoption would significantly hinder the financing of terrorist activities targeting Poland.
According to Tusk, "the overwhelming majority of terrorist operations are based on cryptocurrencies," including acts of sabotage and arson identified by Polish authorities.
"There was no doubt that the method of paying and hiring attackers was based on cryptocurrencies," Tusk said, arguing that a lack of regulation allowed the market to operate with little oversight.
"Russia uses cryptocurrencies as the main ... mechanism for financing this type of operation," he said.
Tusk urged lawmakers to approve the bill on Friday, saying it would help make it harder for Russia to carry out operations against Poland.
He said Poland's intelligence services had been consulted when the legislation was being drafted and had given "an unequivocal opinion" that the bill was necessary "to make it harder to finance terrorist and other criminal activities."
Under Poland's parliamentary procedure, a vote to override a presidential veto amounts to a vote to pass the legislation again. If lawmakers override the veto, the president is required to sign the bill.
Nawrocki in June vetoed legislation designed to regulate the country's cryptocurrency market for a third time, arguing that the proposed rules would overregulate the sector and fail to address concerns previously raised by his office.