Officials have counted more than 6,400 bodies so far and while some officials estimated the final death toll could rise to 20,000 or more, India's defense minister said as many as 100,000 may have died, with twice as many injured.
The Red Cross launched a massive relief operation Tuesday to towns devastated by the quake and appealed for $16 million in emergency aid.
And in a rare gesture of cooperation between fierce rivals, a Pakistani plane landed near the quake's epicenter Tuesday with relief, including 200 tents and 2,500 blankets.
Friday's magnitude 7.9 quake flattened two towns in India's western Gujarat state. Government officials have counted 6,444 dead and 16,557 injured but many bodies remain trapped in the ruins of collapsed buildings.
In the highest estimate from an Indian official, Defense Minister George Fernandes said Tuesday that the death toll could go as high as 100,000, citing the high populations of the two main cities destroyed: Bhuj, with 150,000 inhabitants, and Anjar, with 80,000 people.
"This is my personal assessment," Fernandes told The Associated Press, acknowledging the difficulty of making accurate assessments. "I have been to those areas and I have seen it myself."
The Gujarat state government had a more conservative estimate. Home Minister Haren Pandya said the number of dead would probably be between 15,000 and 20,000.
Damage was estimated at up to $5.5 billion.
Seven cargo planes were due to land in the stricken town of Bhuj throughout the day with water equipment and a 350-bed field hospital. Red Cross experts began to set up an operational center the size of several soccer fields on college grounds just outside Bhuj.
"The needs on the ground are overwhelming the capacity to respond to them," said Denis McClean, spokesman for the International Federation of Red Cross and Red Crescent Societies.
The $16 million would be enough to meet the basic needs of 300,000 people for four months, the Red Cross said.
Rescue workers kept up the grim task of digging into the stony debris of ruined buildings in what they said was an increasingly futile search for survivors. But not without success: 16-year-old Ketan Rathod was pulled from the wreckage alive in Anjar, where he was caught under six feet of concrete with his dead grandmother for 96 hours.
"I was shouting for help or sleeping for most of the time," said Ketan, who could only move a few inches while caught between two pillars at his house. "I was also crying for my grandmother and worried about my parents."
He was found only after the army brought in a crane to start removing heavy slabs of concrete. A soldier heard his cries for help and he was removed from the rubble about 10 a.m.
"When I heard the people digging for me, I started crying," Ketan said. He was dehydrated, but otherwise suffered no serious injuries.
His family had given up hope until the soldiers started shouting that someone was alive.
While the search for survivors continued, workers in Anjar were also beginning to use heavy equipment to clear the debris--a sign that they no longer fear injuring anyone still trapped alive in the ruins.
India's chief regional rival, Pakistan, joined the list of countries offering help to victims Tuesday. The C-130 transport plane arrived in Ahmedabad, the commercial capital of Gujarat state, with about 13 tons of relief goods.
"The havoc wrought by the terrible earthquake ... is a great tragedy," Foreign Minister Abdul Sattar told state-run Pakistan television. "Pakistan wishes to repeat our sense of sadness and grief at the terrible tragedy."
The Pakistani Foreign Ministry said a second relief plane would be sent Wednesday and a third on Thursday.
Pakistan offered help to India soon after the earthquake but said Monday that India had turned down the offer. India denied this, saying New Delhi was willing to accept aid from any country.
The two countries--one overwhelmingly Muslim, the other majority Hindu-- have fought three wars since the creation of Pakistan in 1947 after the partition of British colonial India.
International aid so far includes $5 million in emergency supplies from the United States and $12 million in aid from Britain.