Just three weeks after Turkey was paralyzed by winter storms, raging blizzards have struck again. Thousands of villages across the country have been cut off by heavy snow. Several people have died in weather-related incidents. In Istanbul, driving became almost impossible and schools have been closed for two days. Off the coast, 21 crewmembers of a Cambodian vessel are missing after their boat sank. Several ships have gone down or run aground near Istanbul since Thursday. Air traffic has been badly hit and the city's Ataturk airport was shut down, leaving many passengers stranded. Weather forecasters have predicted heavy snowfall throughout the country over the weekend. Almost zero visibility prompted the closure of the Bosphorus and Dardanelles straits, the only outlet to the world's oceans for Black Sea countries. The storms have not spared neighboring Greece and Bulgaria either. The Acropolis, Athens's most famous landmark, was blanketed in snow and closed off to tourists. Traffic in the Greek capital was reduced to a crawl as temperatures fell to a rare minus three degrees celsius. Meanwhile Bulgaria was forced to close down its largest Black Sea ports at Varna and Burgas. **PHOTO CAPTION*** Snow-covered mosques in Istanbul. Turkey's biggest city was under a state of alert and rescue services were stretched throughout the country as a second day of heavy snow, high winds and freezing weather left homes without power, motorists trapped in unheated vehicles and transport links cut. (AFP/EPA/File/Kerim Okten)