Dense fog on Saturday played havoc with life in north India leading to three train accidents killing ten people, disrupting air and rail traffic and a power break down as the northern grid tripped.

Ten people were killed and 39 injured, 15 of them seriously, in three accidents involving five passenger trains in Uttar Pradesh due to dense fog and near zero-visibility conditions early Saturday.

Eight women and two men, including the Guard of Allahabad— bound Prayagraj Express were among those killed when the Bhiwani-Gorakhpur Gorakhdham Express rammed into it at Panki railway station, about 25 km from Kanpur, Harishchandra Joshi, GM, North Central Railway, Allahabad Zone, said.

The accident took place when the two trains coming from Delhi were on the same track, he said. Though fog appeared to be the reason behind the mishap, an inquiry has been ordered to go into the exact reason behind the accident.

There were also two other rail accidents when the Delhi - Sitamarhi Licchavi Express rammed into the stationary Magadh Express at Sarai Bhopat near Etawah and Sarju Express rammed into a tractor-trolley at an unmanned railway crossing in Pratpgarh, 60 km from Allahabad.

In the two accidents there were no no deaths but one of the drivers was seriously injured.

Delhi, Punjab, Haryana, Chandigarh and parts of Jammu and Kashmir reeled under a power crisis as the northern grid tripped around 3.02 a.m following a technical problem in the transmission lines triggered by the fog and cold conditions.

Areas like Rithala, Shalimar Bagh and many localities in North Delhi plunged into darkness in the wee hours due to the problem. Technical teams of Northern Grid and Delhi Transco are working to restore the lines, a Transco official said.

For the first time this season, air traffic in Delhi suffered severe disruption in flight schedules. Over 90 flights were affected because of thick fog and a cable fault which played havoc with air operations in and out of the IGI airport since the wee hours.

Over 70 domestic flights were delayed, six cancelled and 17 international services diverted to Jaipur, Ahmedabad and Mumbai. Six domestic flights, including those belonging to Jet Airways, JetLite, SpiceJet and Kingfisher, were cancelled, airport sources said.

No no flight could take off or land between 2.00 a.m. and 10.30 a.m. when runway visibility dropped to 100 metres and general visibility to less than 50 metres.

A glitch in cables connected to the Instrument Landing System (ILS) that measures and provides real-time runway visibility data to the Air Traffic Control (ATC) tower also forced the ATC officials to suspend flight operations.

The fog, which was termed by the Met department as most intense during the season, reduced visibility to as low as 50 metres in Delhi on Saturday morning.