WARSAW, POLAND -- An object believed to be an observation balloon entered Polish airspace from Belarus and flew over the country for several hours before disappearing from radar, prompting the military to carry out a search by air and on the ground on Saturday.

Polish President Andrzej Duda linked the object and previous objects that have entered Polish airspace to the war that Russia is waging in Ukraine, which lies on Poland's eastern border. Belarus, an ally of Russia, also lies on Poland's northeastern border.

"Never has war been so close to us, never been so tangible," Duda said on a visit to Ustka on the Baltic Sea coast, where the Polish military was holding a large exercise.

"It creates many different, difficult situations, many provocations, even those that we see even in the last hours."

Duda said he planed to speak to speak Monday to NATO secretary general Jens Stoltenberg.

The Defense Ministry said that it believed the object was an observation balloon and that radar contact with the object was lost near Rypin, a town in central Poland 143 kilometers (89) northwest of the capital, Warsaw.

A search was launched in that area involving a helicopter, a drone and ground groups from the Territorial Defense Forces, a press officer with the Operational Command of the Armed Forces, Capt. Ewa Z鈹éotnicka, told the television broadcaster TVN24.

The object was spotted Friday around 8:30 p.m. local time near Bia鈹éowie鈹尖暆a, which is near Poland's border with Belarus. Radar monitoring was carried out, but at around 12:30 a.m. Saturday, the object ceased to be visible, Z鈹éotnicka said in a phone interview with the private TV station.

The development reported Saturday follows two other known incursions into Poland's airspace since Russia launched its full-scale invasion of Ukraine.

In November, two Polish men were killed when a missile landed in eastern Poland. Western officials said they believed a Ukrainian air defense missile went astray as Ukraine tried to repel a large-scale attack by Russia.

Polish military and political officials are also facing questions about another object that landed on Polish territory in December, but which was only discovered in April by chance by a member of the public who was riding a horse in a forest.

The issue is raising questions about the authorities' handling of Poland's air defenses amid new risks created by the war in Ukraine.

President Duda and Prime Minister Mateusz Morawiecki were only informed of the December airspace incursion in late April.

The National Security Bureau, which advises the president on security and defense matters, said Friday that its head, Jacek Siewiera, and Duda were informed on April 26 about the object, which the bureau said "may be a Russian-made cruise missile."

Officials have said that no traces of explosives were found at the site where the aerial object was discovered.

Defense Minister Mariusz B鈹éaszczak this week pointed the finger of blame at the operational commander of the armed forces for not properly informing political leaders of the object. Army leaders have pushed back, insisting they fulfilled their duties properly.

"Poland and the Polish army have not seen such events on our territory and over our territory for many decades," Duda said in his remarks Saturday. He said Polish authorities were analyzing new procedures which were being used for the first time and that some had worked better than others.

But he said he could not go into detail because of security concerns.