Authorities have issued a wanted notice for the suspect, who they say killed the child "with extreme cruelty."
Prosecutors have pressed charges against the 44-year-old and asked the court to put him under temporary arrest, Polish state news agency PAP reported.
The manhunt was under way on Monday, involving some 1,000 law enforcement officials, including police officers, firefighters and the Polish Navy, according to authorities.
On Sunday, police in Gdynia took to social media to publish the latest photos and CCTV footage of the fugitive, named as Grzegorz Borys, the PAP news agency reported.
Members of the public with knowledge of the man’s whereabouts have been asked to contact police immediately, at 47 7421222 or the emergency helpline 112.
On Friday, police in Gdynia were alerted to the murder of a six-year-old child. A day later, a post-mortem examination confirmed the boy had died as a result of slash wounds to his neck, the PAP news agency reported.
(pm/gs)
Source: PAP, rmf24.pl