Kosiniak-Kamysz, who is also a deputy prime minister, announced the find on the X social media platform.
He said an initial examination indicated the unmanned aircraft, found near Rusinowo, close to the popular coastal resort of Jarosławiec, was a Russian military drone.
Kosiniak-Kamysz said experts were working to secure the site and the recovered equipment.
Deputy Defence Minister Cezary Tomczyk, asked about the incident in parliament on Monday, said that all indications were that the drone was of Russian origin.
He added that Poland was "in many respects a top target for Russian hybrid attacks" and surveillance activities.
"As long as the threat from Russia exists, we will be tested in various ways," Tomczyk said, urging the public to build awareness and resilience.
He said Poland would continue intercepting Russian surveillance aircraft and fighter jets over international waters in its exclusive economic zone.
He said the defence ministry would provide further information if new details about the drone emerged.
Lt. Col. Jacek Goryszewski, a spokesman for the Operational Command of Poland's Armed Forces, said the drone was found in the Baltic Sea by a Navy hydrographic vessel.
Police and military police were at the site, while military bomb-disposal experts were also expected to examine the object.
Authorities suspected the drone had drifted in from international waters, public broadcaster Polish Radio’s IAR news agency
reported.
Lt. Col. Dariusz Rozkosz, a spokesman for the military police's chief commander, confirmed that the object had been located and recovered by the military.
"All services are at the scene — police, military police, border guards and the relevant services for this type of incident," Rozkosz told Poland's PAP news agency.
He said authorities needed to determine whether the aircraft was safe before carrying out a detailed examination and securing it.
At a special security meeting in Warsaw on Sunday evening, Prime Minister Donald Tusk said Russia was escalating its war against Ukraine and that examples of the escalation were appearing increasingly close to Poland's border.
Speaking after Russia struck targets in western Ukraine near the Polish border on Sunday morning, Tusk said Poland would take additional measures to ensure the security of its borders, including closer coordination among the military, police, border guards and customs officials.
Polish systems on Sunday detected an attack involving more than a dozen Geran-5 jet-powered drones in western Ukraine. The Polish military scrambled fighter jets, while authorities warned residents in provinces near the Ukrainian border of a potential threat.
Two drone strikes were reported in close proximity to the Polish border. One damaged a train at the Yahodyn railway station in Ukraine, about 2 kilometres from the border, according to officials.
Ukrainian news outlet Suspilne, citing a deputy director of Ukraine's state railway carrier Ukrzaliznytsia, reported that the train was travelling from Kyiv to Warsaw.
A second drone struck near a gas station close to the Dorohusk-Yahodyn border crossing between Poland and Ukraine, the PAP news agency reported.
Russia launched its full-scale invasion of Ukraine on February 24, 2022, starting the largest armed conflict in Europe since World War II.
(gs)
Source: IAR/PAP