Delhi Metro services were disrupted on Thursday afternoon following a major power failure, an official said.
Curtailed power supply hit both the busy Yellow Line and Blue Line, a spokesman for Delhi Metro said.
The official said power supply was not available from Delhi Transco Ltd due to which the major metro stations at Subhash Nagar, Dwarka, Chhatarpur and Delhi Airport could not feed power to the two lines.
The Yellow Line links Huda City Centre in Gurgaon in Haryana with Samaypur Badli in north Delhi. The much longer Blue Line connects Dwarka in west Delhi with Vaishali and Noida City Centre in Uttar Pradesh.
The official said Metro had curtailed services after drawing power from other sources, affecting frequency of trains.
Commuters said the trains ran at slow speed and stopped longer than normal at various stations during the disruption.
The services were restored after about half hour, officials said.