A second strong earthquake hit Haiti today, waking people from their beds and sending others running into the streets in panic.
The US Geological Survey said the quake measured 6.1, and hit a country already ravaged by an earthquake eight days ago.
The tremor was centered 26 miles north-west of Jacmel, and there were no immediate reports of injuries. The US Geological Survey said the quake struck at a depth of 13.7 miles.
Ed Pilkington, the Guardian correspondent in Port-au-Prince, 35 miles from the epicentre, said this morning's quake was strong enough to be felt in the Haitian capital.
Pilkington tweeted: "just been woken by my bed shaking in #Haiti. another after shock."
The Associated Press said "wails of terror" could be heard from people as they fled buildings already left in ruins by last week's quake. It was not immediately possible to assess what additional damage the new quake may have caused.
Last week's huge quake killed an estimated 200,000 people in Haiti, left 250,000 injured and made 1.5 million people homeless. A massive international aid effort has been launched, but is struggling with overwhelming logistical problems.
Search-and-rescue teams have emerged from the ruins with some improbable success stories including the rescue of 69-year-old woman who said she prayed constantly during her week under the rubble.
Ena Zizi had been at a church meeting at the residence of Haiti's Roman Catholic archbishop when last week's earthquake struck, trapping her. She was rescued yesterday by a Mexican disaster team.
Zizi said that after the quake, she spoke back and forth with a vicar who also was trapped. But after a few days, he fell silent, and she spent the rest of the time praying and waiting.
"I talked only to my boss, God," she said. "And I didn't need any more humans."
Authorities said close to 100 people had been pulled from wrecked buildings by international search-and-rescue teams. Efforts continued, with dozens of teams sifting through Port-au-Prince's crumbled homes and buildings for signs of life. But survivors expressed frustration with the slow pace of the relief effort.
"We need so much. Food, clothes, we need everything. I don't know whose responsibility it is, but they need to give us something soon," said Sophia Eltime, a 29-year-old mother of two who has been living under a bedsheet with seven members of her extended family.
The World Food Programme said more than 250,000 ready-to-eat food rations had been distributed in Haiti by yesterday, reaching only a fraction of the 3 million people thought to be in desperate need.
The WFP said it needs to deliver 100m ready-to-eat rations in the next 30 days. Based on pledges from the US, Italy and Denmark, it has 16m in the pipeline.
So far, international relief efforts have been disorganised, disjointed and insufficient to satisfy the great need. Governments have pledged nearly $1bn (£640m) in aid, and thousands of tons of food and medical supplies have been shipped. But much remains in warehouses, or diverted to the neighboring Dominican Republic. The damaged port and impassable roads complicate efforts to get aid to the people.
The US defence secretary, Robert Gates, said the military will send a port-clearing ship with cranes aboard to Port-au-Prince. It will be used to remove debris that is preventing many larger ships carrying relief supplies from docking.
The UN security council voted unanimously yesterday to approve an additional force of 3,500 police and soldiers for earthquake-devastated Haiti, amid rising concern over outbreaks of looting by desperate survivors and the re-emergence of notorious gang leaders who escaped when the country's prisons collapsed.