Tripoli, Libya (CNN) -- Libyan refugees who fled to Italy said a severely overcrowded boat with hundreds of people on board capsized near the harbor of Tripoli, a spokeswoman for the United Nations' refugee agency said Tuesday.
Laura Boldrini, spokeswoman for the U.N. High Commissioner for Refugees in Italy, told CNN she received reports from Libyan refugees who arrived Saturday in Lampedusa -- an island south of mainland Italy -- that they witnessed a boat with possibly more that 600 refugees on board capsizing.
Boldrini said refugees who arrived in Lampedusa on separate boats described a horrific scene in which hundreds of people were thrown into the water. She said several of the refugees were trying to reach family members who had been on board the capsized vessel.
The Somali ambassador in Tripoli confirmed to the UNHCR that 16 dead bodies had been pulled out of the water from the harbor, Boldrini said. The total number of causalities is unknown.
The crisis in Libya has prompted many to try to escape, according to Valerie Amos, the U.N. undersecretary-general for humanitarian affairs.
Almost 750,000 people have fled the country, another 58,000 are displaced within Libya and another 5,000 are stranded at border crossings into Libya, Tunisia and Niger, Amos told the U.N. Security Council on Monday.
On Tuesday, NATO airstrikes shook Tripoli after the alliance's secretary-general dismissed complaints that the allied campaign against longtime Libyan strongman Moammar Gadhafi had fallen into a stalemate.
At least three rounds of explosions echoed across the Libyan capital in a three-hour span that began late Monday, and the roar of jets could be heard overhead.
Government spokesman Musa Ibrahim told CNN that the strikes hit administrative buildings in central Tripoli, and that a nearby hospital was "indirectly" affected.
Ibrahim said the strikes followed "an extended period of calm."
"It is very sad," he said. "We are losing people every day on both sides. We think it is time to sit down and talk."
NATO warplanes and missiles have been pounding Gadhafi's forces and government installations since March as Gadhafi tries to quash a nearly three-month-old revolt against his regime. Libyan rebels are demanding freedom and an end to Gadhafi's nearly 42-year-rule.
NATO is operating under a U.N. Security Council resolution authorizing any means necessary -- short of invasion -- to protect civilians.
Meanwhile, an aid ship chartered by the International Committee of the Red Cross reached the war-torn port city of Misrata on Tuesday, the organization said in a statement. Misrata is the only city in western Libya held by the rebels, and witnesses have said indiscriminate shelling on the city has left victims with crushed bones, burns and amputations.
The ICRC is bringing medical supplies, spare parts to repair water and electrical supply systems and 8,000 jars of baby food, the statement said.
The situation in Misrata "is at the forefront" of U.N. concerns about Libya's civilian population, Valerie Amos, the U.N. undersecretary-general for humanitarian affairs, told the Security Council on Monday. Two months of fighting and the ongoing shelling of the city's port had prevented aid ships from docking there, and between 150 and 300 non-Libyans were still waiting to be evacuated, she said.
"Some people are running short of food, water and other basics," she said. "Medical facilities need supplies and more trained personnel."
Amos said the fighting and sanctions imposed on Gadhafi and his allies have caused "a severe disruption of supply lines within the country." The results have been "shortages of fuel, difficulties in obtaining commodities including foodstuffs, medicines and other essential goods, and there have been severe cash shortages throughout the country."
Amos said western Libya has about three months' supply of food remaining, and the mostly rebel-held east has about two months. Fuel and supplies for desalinization plants and other facilities that provide fresh water to many Libyans "are running out," she added.
Amnesty International has said Gadhafi's attacks in the port city may amount to war crimes.
A report issued last week by the monitoring group accused pro-Gadhafi forces of the "unlawful killing of civilians due to indiscriminate attacks, including use of heavy artillery, rockets and cluster bombs in civilian areas and sniper fire against residents."
Secretary-General Anders Fogh Rasmussen told CNN on Monday that Gadhafi and his regime "have no future," but refused to predict how long the Libyan leader could hold on.
Rasmussen denied that the situation in Libya had devolved into a "stalemate," insisting that NATO was "making progress" and had "taken out" a substantial part of Gadhafi's military capability. He said a political solution was required to bring the conflict to an end, but "it's hard to imagine an end to the violence as long as Gadhafi remains in power."