Warsaw - Twenty-one people were killed and some 20 others injured when a hostel for the homeless burned down Monday in north- western Poland. Seventy-seven people were registered in the hostel in the Baltic Sea coastal town of Kamien Pomorski, some 500 kilometres north-west of the capital Warsaw.

The fire was so ferocious and spread so greatly that there was no hope of extinguishing it and rescuers concentrated on saving people from the flames, a firefighter told TVN24.

Witnesses said some hostel residents were hurt when they jumped from windows. An eight-month-old baby was among the injured, TVN24 reported.

Police and prosecutors were on the scene investigating to try to determine the cause of the fire, one of the worst in recent Polish history.

On Monday afternoon Prime Minister Donald Tusk visited the scene, while President Lech Kaczynski has declared a three-day period of national mourning.

"I can guarantee that help will be complete and enough when it comes to ensuring a place to live for those saved from this catastrophe," Tusk told the Polish Press Agency PAP, having broken off from his own Easter holiday to visit the scene of the tragedy.

Residents of the small town were first to pitch in with help, TVN24 reported, and donated clothes, food and toiletries to those left with nothing after the fires. Survivors were taken to nearby hotels.

The Polish government promised to rebuild the hostel, at costs of up to 4 million zloty (1.2 million dollars), PAP reported.(dpa)