Police are detaining a growing number of photographers while taking pictures on the streets of New York as part of anti-terrorism measures, according to television channel NY1.

In one such case photographer James Corporan said police held him for 45 minutes after he refused a police officer?s request to delete photos he had taken of an overpass in the South Bronx.

Two days later the police questioned him again.

?They asked me if I was a member of any political or social organisations and they asked me if I was Muslim,? the photographer told NY1.

An increased number of similar cases is reported to have prompted an investigation by The New York Civil Liberties Union (NYCLU).

?We have been told that the number one complaint coming into the New York Police Department (NYPD) terrorism hotline are photography reports,? said NYCLU spokesman Chris Dunn, adding: ?We therefore believe there are a number of photographers who are being investigated by the NYPD and we believe there are no guidelines or specific training about how to deal with photographers.?

In a statement released to NY1 the NYPD said: ?While photography is a common element in reports to the police counter terrorism hotline, we don?t prohibit it. We may make enquiries when suspicious activity or trespassing is reported.?

In March photographers claimed a victory over New York police when they forced the Metropolitan Transportation Authority to state in writing that there is ?no ban on photography? on the city?s subway and overground train networks.

The move followed growing numbers of reports from photographers claiming that police had threatened to arrest them for taking pictures in public places, apparently telling them that ?photography is illegal?.

The NYCLU, supported by the National Press Photographers Association and the New York Press Photographers Association, threatened a lawsuit against the Metropolitan Transportation Authority.