"As things are unfolding, the death toll may climb up to the 2000 mark," said Akhtar, a principal secretary in the Jammu and Kashmir chief minister's office.
"We don't know anything about 10,000 people living in the upper reaches of the Tangdhar area," he said referring to a mountainous region in Kupwara district on the India-Pakistan frontier.
"There are about a dozen big border villages perched on mountain tops still inaccessible in both Uri and Tangdhar areas due to road connectivity," Akhtar said.
There was also a threat of flooding in Tangdhar as a landslide had blocked the Kishanganga river.
Victims in many remote areas have complained that relief efforts were slow and senior government officials said work had been hampered due to communication problems.
Indian soldiers searched for isolated villages believed buried under landslides, but their efforts have been hindered by sporadic militant attacks, officials said.
Thousands of people across the Kashmir Valley spent Sunday night in the open after mosques across the region made announcements over their public address systems at around 10.30pm (1730 GMT) that fresh tremors were expected.
The authorities said the announcements were triggered by rumours circulated through mobile phone text messages.
"When I heard the announcements, I thought a fire had broken out in the area. But it was actually about another earthquake," said Bashir Ahmed, a resident of Srinagar, the main city of Indian-administered Kashmir.
"We don't know anything about 10,000 people living in the upper reaches of the Tangdhar area"
Naeem Akhtar, a principal secretary in the Jammu and Kashmir chief minister's office
"So I ran out of my bedroom and into the open compound. The announcements went on through the night," he said.
Historic bridge damaged
Defence authorities said that the Peace Bridge that marks the India-Pakistan ceasefire line and connects the only highway between the two Kashmirs was damaged by the quake and was unfit for traffic.
The bridge was opened in April when India and Pakistan reopened the Srinagar-Muzaffarabad road for the first time in nearly 60 years.
Thousands of people have been injured by the 7.6 magnitude earthquake, centred across the frontier in Pakistani Kashmir, and many more houses destroyed or damaged across the Himalayan region.
More than 20,000 people were feared killed in Pakistan.
Soldiers involved in the search and rescue operation have fought armed rebels and in the worst encounter late on Saturday eight guerrillas were killed in a gun battle.
The Kashmir dispute is at the
heart of India-Pakistan enmity
Soldiers ran into the men trying to infiltrate into Indian-administered Kashmir from the Pakistani side near the ski resort of Gulmarg in Baramulla district.
Elsewhere, guerrillas shot dead 10 Hindus in two separate attacks late on Sunday on remote villages in Rajouri district, also affected by the earthquake.
Rajouri is about 170km north of Jammu, Indian Kashmir's winter capital.
The territorial dispute over Kashmir is at the heart of decades of India-Pakistan enmity and the Indian-administered part of the Himalayan region is also torn by a 16-year Islamist revolt against New Delhi's rule.
Tens of thousands of people have been killed in violence.