A woman carries a sack of rice during a food distribution organized by the U.N. under U.S. army security control in downtown Port-au-Prince on Sunday. (Eduardo Munoz/Reuters)

Relief workers began handing out women-only food coupons in Haiti on Sunday in an effort to ensure earthquake relief supplies reach the neediest families.

The United Nations World Food Program (WFP) implemented the new distribution plan at 16 sites in the capital, Port-au-Prince, after workers reported that young men were often swarming aid trucks and pushing ahead of women in lineups.

The WFP said the coupons will go to women because they tend to be responsible for the household food supply. The aim is to reach two million people over two weeks.

Each distribution centre will receive 42 tonnes of rice and each family will receive a 25-kilogram ration, with only women being allowed into distribution sites to collect their share.

The WFP and its partners are promising to work with local authorities to ensure that men in need of assistance are not excluded.

The latest approach to food distribution comes almost three weeks after a 7.0-magnitude earthquake reduced Port-au-Prince and other cities to rubble and killed as many as 200,000 people.

Doctors send victims to U.S.

Also on Sunday, doctors skirted the U.S. military's suspension of medical evacuation flights by flying three critically ill victims of Haiti's quake to U.S. hospitals on a private jet.

A five-year-old tetanus victim, a 14-month-old boy with pneumonia and a baby boy with third-degree burns were sent to Children's Hospital in Philadelphia by the Boston-based aid group Partners in Health.

The U.S. military stopped medical evacuation flights Wednesday because of apparent concerns over where to put the patients and perhaps over how to pay for them. Hundreds of other patients need treatment abroad, doctors in Haiti said.

The U.S. Army Corps of Engineers has been asked to build a 250-bed tent hospital to relieve pressure on a U.S. navy hospital ship and on Haitian facilities where quake victims are being treated under tarpaulins in hospital grounds.

Several Port-au-Prince hospitals were damaged or destroyed.

With files from The Associated Press