Exhausted, wearing winter coats to protect them against near-freezing temperatures, women and children continue to cross into Poland from Ukraine on Monday, through the main border crossing of Medyka.

Some were greeted by waiting relatives and friends.

Others headed to reception centers organised by neighboring governments.

The U.N. refugee agency said Monday that more than 500,000 people have fled Ukraine since Russia invaded the country last week.

Poland's border guards said some 156,000 people have entered from Ukraine since Thursday.