NEW YORK - KAZAKH supermodel Ruslana Korshunova's fatal fall from her balcony was a suicide, officials ruled, though friends told local media she was in good spirits and suicide seemed incomprehensible.

Korshunova, 20, was discovered dead in front of her apartment building in downtown Manhattan, near the financial district and South Street Seaport tourist area on Saturday afternoon. Several eyewitnesses saw her plunge from a ninth-floor balcony.

Authorities ruled the model's death a suicide on Sunday, saying Korshunova died from blunt impact injuries, a spokesman for the city's medical examiner told The New York Daily News.

Media reports, citing police sources, said there was no sign of a struggle inside her apartment, but at least one friend expressed disbelief.

'There's no way she would have killed herself,' said Ms Kira Titeneva, who described Korshunova as her best friend. 'I talked to her (Friday) night and we were talking all the gossip,' she told the News.

Another friend told The New York Post Korshunova had just returned from a modelling job in Paris and seemed 'on top of the world. ... There were no signs', the unidentified friend said.

'I don't see one reason why she would do that.'

Korshunova, a native of Kazakhstan, had been profiled in British Vogue in recent years as a new face to watch, and she was featured in ads by Vera Wang, Marc Jacobs, Christian Dior and DKNY.

A spokesman for Korshunova's agency, IMG, which also handles Heidi Klum and Kate Moss, said 'We're shocked and our heart goes out to her family.'