UN, coast guard say boat with 50 migrants capsizes off Libya The U.N. refugee agency and the country's coast guard says a boat carrying at least 50 Europe-bound migrants has capsized in the Mediterranean Sea off Libya

CAIRO -- A boat carrying at least 50 Europe-bound migrants capsized Saturday in the Mediterranean Sea off Libya, the U.N. refugee agency and the country's coast guard said, while an independent support group said another 56 migrants on another boat were "at risk" in the sea.

Coast guard spokesman Ayoub Gassim told The Associated Press that a shipwreck took place off the western city of Misrata, 187 kilometers (116 miles) east of the capital, Tripoli.

UNHCR said rescue efforts were ongoing Saturday afternoon, and released no details on casualties.

Alarm Phone, an independent support group for people crossing the Mediterranean, said a second boat for migrants was in destress, with "about 56 lives at risk."

The group said it received a call from migrants on the boat, who left Libya's shores days ago, saying that "they are desperately calling for help and are afraid to die."

"They are still in distress at sea with no rescue in sight. They have now been at sea for over 60 hours," Alarm Phone said.

Libya became a major crossing point for migrants to Europe after the overthrow and death of longtime dictator Moammar Gadhafi in 2011, when the North African nation was thrown into chaos, armed militias proliferated and central authority collapsed.

In recent years, the European Union has partnered with the coast guard and other Libyan forces to try to stop the dangerous sea crossings.

Rights groups say those efforts have left migrants at the mercy of brutal armed groups or confined in squalid detention centers that lack adequate food and water.

At least 6,000 migrants from Eritrea, Ethiopia, Somalia, Sudan and other nations are locked in dozens of detention facilities in Libya run by militias accused of torture and other abuses.

There are limited supplies for the migrants, who often end up there after arduous journeys at the mercy of abusive traffickers who hold them for ransom from their families.