Anti-terror searches continuing
Police are continuing to search 10 properties across the north-west of England in connection with an alleged planned terror attack.
Twelve men - 11 of them Pakistani and most of them students - are still being questioned over the alleged plot.
Photographs found at one location are being examined, the BBC has learned.
Downing Street said Gordon Brown has spoken to Pakistani President Asif Ali Zardari, who are both "committed to work together" to combat terrorism.
Police arrested the 12 suspects during a series of raids in Manchester, Liverpool and Clitheroe in Lancashire.
The planned operation had to be brought forward to Wednesday following a security blunder by Britain's anti-terror chief.
Assistant Commissioner Bob Quick had been photographed carrying documents with details of the alleged plot clearly visible. He resigned on Thursday.
Since the raids, forensic officers have been gathering evidence at 14 properties in north-west England and taking away vehicles for examination.
Senior officers have insisted there was no intelligence pointing to any specific targets.
But the BBC's Nick Ravenscroft said sources had confirmed that photographs of four popular Manchester locations were recovered during searches.
These were the Arndale and Trafford Centre shopping complexes, Birdcage nightclub and St Ann's Square. THE BBC