In nine seconds flat, two skyscrapers built illegally in the city of Noida near the Indian capital some nine years ago were razed by a controlled explosion on Sunday afternoon.

Exactly at 2.30 pm, the 40-storey twin towers -- Apex and Ceyane -- were brought down with the use of 3,700kg of explosives, as millions of Indians glued to their TV sets to watch the spectacle live.

The twin towers became the country's largest ever highrises to be imploded.

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India's Supreme Court, in August last year, ordered the demolition of the twin towers built by private developer Supertech for violation of various building norms.

Utkarsh Mehta of Edifice Engineering, the company entrusted with the demolition job, said, "As expected, the explosion triggered vibrations like that of a minor earthquake. We achieved 100% success."

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Local civic authorities had earlier ensured the evacuation of residents of all housing societies in the vicinity of the twin towers. Stray dogs were also shifted to animal shelters, officials said.

"The nearby Noida Expressway was shut for 45 minutes for the demolition. Hospitals in the city were on alert and 8-10 ambulances kept at standby in case of any untoward situation," a police officer said.

Demolitions of highrises are rare in India. Two years ago, authorities in the southern state of Kerala razed two luxury waterfront highrises for flouting environmental norms.