NEW YORK, Oct 8: New York City is bracing for a possible subway attack on its extensive subway network since two of the dates mentioned in intelligence about possible subway attacks in New York were Friday and Sunday, officials told reporters on Saturday.

The officials said the source of the threat had trained at a camp in Afghanistan and has been an accurate purveyor of information to US intelligence in the past.

The source passed a polygraph test having to do with knowledge of the possible attacks in New York, one of the officials said.

According to law enforcement sources, the information garnered from the individual in Iraq claimed that a group of 15 to 20 people were in the United States to carry out attacks in New York.

That information, the sources said on Friday, led to a military operation on Wednesday night in Musayyib, 70kms south of Baghdad, where three Al Qaeda suspects were arrested.

Police at subway stations rummaged through briefcases, purses and bags, and two rush-hour false alarms intensified tension across the city.

New York has been on orange alert — the second-highest level – since the colour-coded warning system was established after the Sept 11, 2001, attacks.

The announcement of a possible attack on New York’s subway system prompted San Francisco’s Bay Area Rapid Transit to raise its alert, from orange to ‘enhanced orange’ on Friday.