Footage of police raiding a flat in Cheetham Hill on Wednesday
Police are continuing to search 10 properties across the north-west of England in connection with an alleged planned terror bomb attack.
They have found pictures of popular Manchester shopping centres and a nightclub, the BBC has learned.
Twelve men - 11 of them Pakistani, and most of them students - are still being questioned over the alleged plot.
Gordon Brown and Pakistan's president are "committed to working together" to combat terror, says Downing Street.
Although the police previously insisted there was no intelligence pointing to any specific targets, sources have told the BBC photographs of four popular Manchester locations were recovered during searches.
Last year over 10,000 students were admitted from Pakistan with what are clearly inadequate checks
These were the Arndale and Trafford Centre shopping complexes, Birdcage nightclub and St Ann's Square.
On Thursday, security staff at the Trafford Centre and officials at Manchester Arndale said they had not been informed of any threat.
An Arndale spokesman said: "Both Manchester Arndale and the The Birdcage will be operating as normal over the Easter weekend."
Police are not thought to have recovered any explosive devices during their searches, and BBC security correspondent Frank Gardner said his understanding was that the alleged plot had been at the "aspirational, not operational" stage.
As the searches continued in Manchester, Merseyside and Lancashire, the political focus moved to Britain's border security, amid revelations that most of the arrested men were Pakistani nationals who entered the UK on student visas.
The prime minister has already called on Pakistan to do more to weed out potential extremists who might target the UK.
Downing Street appeared keen to emphasise the fact that talks between the UK and Pakistan were continuing at the highest level.
A spokesman confirmed Mr Brown and President Asif Ali Zardari had spoken on the telephone on Wednesday evening.
"We need all the co-operation that we have with the Pakistani authorities" - courtesy of Frost Over the World, Al-Jazeera English
"They agreed that the UK and Pakistan share a serious threat from terrorism and violent extremism, and committed to work together to address this common challenge," said the spokesman.
Meanwhile, critics accused the government of not doing enough to weed out potential extremists amongst the thousands of Pakistanis who enter the UK on student visas.
An estimated 42,000 Pakistanis came to Britain on student visas between April 2004 and April 2008 - the last year for which figures are available.
Immigration minister Phil Woolas insisted that changes brought in by the government meant that anyone applying for a student visa from countries like Pakistan must now undergo strict vetting procedures.
These include photograph and fingerprint checks as well as the requirement to supply identification and other documents.
"We also use intelligence from our own services and from overseas countries in a targeted way," Mr Woolas said.
The minister also rejected criticism from Pakistan's High Commissioner, Wajid Shamsul Hasan, who said Pakistani authorities were being stopped from helping to carry out background checks.
"It's naive to think that we don't check, we do work very closely with the Pakistan authorities, indeed we've been criticised for doing so," Mr Woolas told the BBC.
Shadow home secretary Chris Grayling said background checks on students coming to Britain from countries linked to terror needed to be improved.
And Migrationwatch UK chairman Sir Andrew Green said student visas continued to be a "gaping hole" in Britain's borders.
"Applicants from countries of concern like Pakistan and North Africa should be given a full interview by a UK-based visa officer and only admitted if they can demonstrate that they are genuine," he said.
"Last year over 10,000 students were admitted from Pakistan with what are clearly inadequate checks."
Pictures of Manchester's Arndale Centre are thought to have been found
But Muslim spokesman Mohammed Shafiq, of the Manchester-based Ramadhan Foundation, said: "Most visitors and students to the UK are peaceful people that abhor terrorism and we should not tarnish all Pakistanis or Muslims because of the actions of a small minority."
The Home Office said biometric [fingerprint] and other checks had been introduced specifically for Pakistani nationals applying for UK student visas in September 2007.
From autumn this year, British universities will also obliged to check the names of overseas students against a government database of terror suspects.
So far it is not known whether any of the suspects arrested on Wednesday applied for their overseas student visas after September 2007 - which could mean they passed the tests.
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