A Polish NGO rescued two Syrian migrants late on Sunday, after the brothers crossed the border from Belarus and made it some 40 kilometers (24.85 miles) into Polish territory.
Thousands of migrants have traveled to Belarus in the hope of crossing into the European Union (EU), only to find themselves trapped on the border in freezing conditions.
Reuters witnesses said brothers Kader, 39 and Loas, 41, from Homs, were almost unconscious and too tired to speak when medics arrived to help them near the village of Topczykaly. The surname of the two brothers has not been released.
"We found two men in the woods, and they are in a really bad condition, and they couldn't communicate with us," said Agata Kolodziej from Polish charity Ocalenie Foundation.
"We couldn't really get any information out of them, except their names, so we decided to call an ambulance."
The ambulance and Polish police arrived at the scene shortly after. Kolodziej said the brothers, who had spent four days in the forest, were being taken to hospital.
Polish police said on Saturday the body of a young Syrian man had been found near the border. At least eight migrants have already died and fears are growing for the safety of others as harsh winter conditions set in.