International aid agencies are urging the authorities in the tsunami-stricken Andaman and Nicobar Islands to let them join the relief effort there.
Homeless tribals on Car Nicobar island in a makeshift camp
Much of the Andamans is off-limits to foreigners because of security concerns and to protect aboriginal tribes from outside influences.
A senior Oxfam official says the policy means that "valuable time" is being lost in the aid effort.
More than 6,000 people in the area are confirmed dead or missing.
But there is no confirmation of the fate of at least 10,000 others still unaccounted for.
"This closed-door approach of not allowing [foreign aid agencies] is delaying relief efforts," Shaheen Nilofer, the head of Oxfam's operations in eastern India said, the Associated Press news agency reports.
ANDAMAN AND NICOBAR
About 400 islands, 38 inhabited
Islands are peaks of submerged mountain range
Indian territory, area of 8,249 sq km
Population around 370,000, about 100,000 in Port Blair
Number of tribes, including Jarawas, Onges and Shompens
"Valuable time has been lost because of this delay. [India is] accelerating the miseries of the poor people... Somewhere, someone has to be responsible."
In the Indian capital, Delhi, Oxfam spokeswoman Aditi Kapoor told the BBC: "We would like to work in cooperation with the authorities in the Andamans."
Medecins Sans Frontieres was the first international aid agency to get relief supplies to the Andamans.
The BBC's Subir Bhaumik, in the capital Port Blair, says the supplies are still lying in the airport there.
MSF's head of operations in India, Stuart Zimble, told the BBC: "We remain optimistic the government will allow our team of doctors to get to the outlying islands and administer medical care."
Some 400,000 people live on the Andamans archipelago, which comprises more than 300 islands and islets and some 200 rocky outcrops.
The ban on foreigners visiting much of the Andamans is partly because India has an important military base on Car Nicobar island that was devastated by the tsunami, with heavy loss of life.
In addition the islands are home to a number of tribes who make up some of the most primitive peoples on the planet.
Foreigners are not allowed access to the areas where they live.
"We can understand the sensitivity of the Indian government, but we are prepared to work together with the administration," Stuart Zimble said.
"We want our doctors to team up with local doctors and spread out into the islands so that we can save a many people as possible."
US officials say they will begin a major relief work "the moment we have permission".
The Indian military distributing aid on one of the islands
"We hope we will be allowed to join the relief effort," Souribh Sen of the US consulate in Calcutta told the BBC.
A team from the United Nations children's agency, Unicef, now in Port Blair, says the authorities asked them to bring supplies of oral saline and lactate, indicating fears of outbreaks of cholera.
The Indian army said on Sunday that planes had dropped food and water to tsunami survivors on all the inhabited islands in the Andamans and Nicobar chain.
Outbreaks of disease have been reported on remote southern islands.
Our correspondent says aid workers have been worried about possible outbreaks of water-borne diseases because the tsunami polluted wells and other sources of drinking water.
Earlier on Sunday, the military commander in charge of the relief effort said the most remote locations had now been reached.
More than 3,000 people were evacuated to the mainland and relief camps in Port Blair on Friday.
Relief efforts in the archipelago's 38 inhabited islands have been hampered by the destruction of most of the islands' jetties.
The island chain, close to the epicentre of last Sunday's earthquake, has also felt a number of aftershocks.
On the Indian mainland, aid operations are stepping up in the south.
A mother in Tamil Nadu mourns for her lost daughter
In Tamil Nadu more bodies of the estimated 10,000 from the region were being cremated or buried on Monday.
Clinics and vaccination centres are being set up while government officials say they will ease rules on compensation for people who have lost livelihoods or members of their families.
The BBC's Daniel Lak says that in the port town of Nagappattinam, one of the worst affected areas, much of the aid is arriving from informal sources such as businesses, community groups and individuals.
The death toll there is expected to climb as Indian navy vessels and scuba divers comb river and sea bottoms for missing fishermen who were at sea when the tsunamis hit.
One problem plaguing the aid effort, say relief workers, has been the number of official visits by dignitaries and high government people.
Each visit takes hundreds of police officers and workers to coordinate, people that might better be part of the direct relief effort.