NEW DELHI, Jan. 6 -- Some 150 flights were severely hit due to dense fog which enveloped the Indian capital since late Sunday night, a senior aviation official said Monday.

"A total of 150 domestic and international flights have been affected. While a large number of domestic and international flights to the Indira Gandhi International Airport were diverted to other cities, others have been delayed as the runaway visibility dropped below 50 meters due to thick fog," the official said.

The fog set in at the airport around 9.30 p.m. Sunday and stayed till 3.30 a.m. this morning, he added.

Meanwhile, some 40 trains to the national capital have also been running behind schedule and 10 others to different parts of northern India were delayed due to the fog, a senior Indian Railways official said.

The Indian Meteorological Department has predicted clear sky later in the day.

Fog is common in northern India during the winter months of December and January.