A bomb threat at Delhi airport has led to the grounding of an Air India flight which was on its way to Hong Kong.

The threat turned out to be a hoax but all 178 passengers on board the aircraft were evacuated.

Officials say a call received in Hong Kong said two passengers on board the flight were carrying explosives.

There was information that there were terrorists on board but it has been declared a hoax

Aviation Minister Shahnawaz Hussain

It is the third security incident at Delhi airport this week

The Air India jet was on a routine flight from Bombay, also known as Mumbai, to Hong Kong via Delhi.

After airport officials were alerted to the bomb threat, the aircraft was taken to an isolated bay and the passengers evacuated.

"There was information that there were terrorists on board but it has been declared a hoax," India's Civil Aviation Minister, Shahnawaz Hussain, said.

The minister said he has now called for an investigation following an increase in hoax calls in recent weeks.

Security scares

Two days ago, a British Airways flight from Singapore to London made an emergency landing in Delhi following a bomb scare.

Airline crew became suspicious after the discovery of a packet on board which later turned out to be a toilet case.

On Monday, a man was taken off a Biman Bangladesh Airlines flight from Dhaka to Delhi on suspicions of being a "terrorist".

He was questioned by police and is said to be facing charges of travelling on a false passport.

And on Sunday, an Indian Airlines flight in the eastern city of Patna was grounded following a bomb scare that also turned out to be a hoax.