A military plane crashed in a forested area in northwestern Poland, killing 20 people, the prime minister said early Thursday. The officers had been attending a flight safety conference in Warsaw.

Prime Minister Donald Tusk said the plane crash, which occurred as it was about to land Wednesday evening. The 20 victims included a brigadier general and four crew members, he said.

"Soldiers, husbands, and fathers have died, and that is the most tragic result of this catastrophe," said Tusk, who had rushed to the site of the accident.

He called it a "huge loss for the Polish air force."

The air force plane carrying 16 passengers and four crew members was approaching an air force airstrip at Miroslawiec shortly after 7 p.m. (1800 GMT) when it crashed in a forested area.

The aircraft, a Spanish-built CASA C-295M military transport plane, was about 3 kilometers (2 miles) from the airstrip when it clipped trees on its approach, crashed into a wooded area and burst into flames, officials said.

Officials did not say what caused the crash.

The plane originally had more people on board when it took off from Warsaw, but had already landed at three other military airports -- in Powidz, Poznan and Krzesiny -- to return soldiers to their home bases. It had two more planned stops to make, in Swidwin and Krakow.

Tusk said it was ominous that the victims "were returning to their units from a conference devoted ... to flight safety."

Polish media described the accident as one of the worst military disasters in more than three decades, and President Lech Kaczynski, on a visit to Croatia, was cutting short his trip to return to Poland on Thursday, a spokesman said.

Among those killed were Brig. Gen. Andrzej Andrzejewski, commander of an air brigade based in Swidwin, as well as the commander of the Miroslawiec air base, Lt. Jerzy Pilat, said Defense Minister Bogdan Klich, who rushed to the site of the accident along with the prime minister.