The United Nations Security Council has voted to send 3,500 more UN troops and police to quake-hit Haiti amid scenes of lawlessness in the stricken capital Port-au-Prince.
Meanwhile, the US boosted its troops there, led by Marines who descended from helicopters, as the military ramped up a huge aid operation for desperate Haitians.
In a spectacular move, paratroopers from the 82nd Airborne division on Tuesday landed in at least four choppers to secure the ruined presidential palace, a once elegant white building now surrounded by a squalid refugee camp.
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They were sent to help maintain order and protect humanitarian convoys, as the estimated death toll from last Tuesday's 7.0 quake rose to 75,000.
The UN announcement came as the United States Coast Guard also called up 900 reserve troops, many for deployment on hospital ships.
UN officials stressed that the division of labour between UN and US forces in the region was clear.
The US military also began airdrops of food and water to survivors in areas that are too dangerous for aid workers on the ground.
A US air force plane dropped some 14,500 meals and 15,000 litres of water to a site just outside Port-au-Prince, the Pentagon said in a statement.
The US military had been reluctant to make aid airdrops due to concerns they would spark fierce scuffles on the ground, but said the airdrop was made to a 'controlled drop zone' where no people on the ground were endangered.
As chaos reigned in Port-au-Prince, Haitina police shot dead a 15-year-old girl as they fired warning shots at looters.
The 15-member UN Security Council, "recognizing the dire circumstances and urgent need for a response," on Tuesday endorsed Secretary-General Ban Ki-moon's request for reinforcements.
The resolution decided that the UN mission in Haiti (MINUSTAH), which had its headquarters destroyed in the January 12 quake, "will consist of a military component of up to 8,940 troops of all ranks and of a police component of up to 3,711."
China's UN Ambassador Zhang Yesui, the council chair this month, said the extra troops and police would be deployed for a period of six months.
The council vote came exactly a week after the quake struck the impoverished Caribbean nation of nine million peoplethe UN confirmed at least 46 staffers had been killed with more than 500 missing.
"I am grateful to to the Security Council for its swift action, Ban told reporters, adding that the council sent "a clear signal that the world is with Haiti."
"We must do all we can to get these extra forces on the ground as soon as possible so that they can help maintain order and deliver humanitarian assistance," he added.
Ban briefed the Council during a six-hour visit to Port-au-Prince on Sunday, and expressed solidarity with quake victims and shell-shocked UN staff.
"Our chief priority is to get the relief distribution in Port-au-Prince fully operational so that we may more efficiently distribute supplies: food, water, medicines, tents," the UN boss said.
Ban's call came amid fears that survivors' desperation over the slow pace of aid could spill over into widespread violence, in a country that has long-running security troubles.
Thousands of homeless Haitians were prey to roving bands of looters swarming through the ruins of Port-au-Prince, with police and military officials tasked with protecting the vulnerable populace nowhere to be found.
French Ambassador Gerard Araud said the Security Council would also have to examine MINUSTAH's mandate in the near future, "to see what is necessary to adjust it to the new situation."
Extra troops would remain in Haiti in case the security situation deteriorated, the UN announced.
