"This avalanche hit a (military) headquarters. Over 100 soldiers and personnel are trapped," army spokesman Major-General Athar Abbas told Reuters, adding that a total of 117 soldiers were stationed there.
A helicopter rescue team was searching for survivors with sniffer dogs, he added. "This happened at six o'clock. These avalanches usually happen at night. It took them by surprise," said Abbas.
Siachen is in the northern part of the Himalayan region of Kashmir.
Muslim-majority Kashmir is at the heart of hostility between India and Pakistan and was the cause of two of their three wars. The fourth was over the founding of Bangladesh.
Described as the world's highest battlefield, for two decades India and Pakistan fought at altitudes of over 20,000 feet in minus 60 degrees Celsius temperatures.
Indian and Pakistani forces, estimated to number between 10,000 and 20,000 troops combined, still face off against each other in mountains above the glacier. More