Police searched a number of properties in Liverpool and Manchester
Two Pakistani students arrested over an alleged terror plot have returned to Pakistan after deciding to leave the UK voluntarily, the Home Office has said.
Abdul Khan, 26, and Shoaib Khan, 27, were among 12 people held by police after raids in north-west England in April, but the pair were never charged.
The Home Office tried to deport them, saying they remained a security threat.
It is understood the men decided to leave after being denied bail while appealing against deportation.
The appeal was due to be heard by the Special Immigration Appeals Commission (Siac) in March next year.
Both students, who had been Category A prisoners at HMP Manchester, arrived in Islamabad on Saturday.
Abdul Khan said his detention had been "like a hell" and his treatment showed the British authorities "do not know what justice means".
The men's solicitor, Amjad Malik, said his clients should have been freed instead of being held for months.
He said the students would continue to fight their case in Britain and had taken up the issue with Pakistan's interior ministry.
Mr Malik claimed both men had been frequently strip-searched, subjected to "searches by dogs" and served tainted food.
The British High Commission in Pakistan has rejected the allegations as "unfounded".
It said that apart from one incident of allegedly contaminated baked beans, no other complaints had been made during their detention.
"The UK government treats all those in detention in UK prisons fairly and humanely, regardless of their nationality, race or religion," a statement said.
Twelve students were arrested in the terror raids in Manchester and Liverpool as part of Operation Pathway, with three subsequently released.
The anti-terror operation had to be brought forward after Britain's most senior counter-terrorism officer, Bob Quick, was photographed with a secret document. He subsequently resigned.
The Home Office is attempting to deport two others, Sultan Sher and Janus Khan, on the grounds of visa irregularities after dropping claims that they posed a threat to national security.
Five more, referred to only as VE, UF, ZA, YB and XC, are to appear before Siac for their deportation appeal hearing on March 10.
Evidence passed to the tribunal claimed one of the men, who cannot be identified, exchanged e-mails with an associate of al-Qaeda.
MI5 analysis also suggested girls' names were used as code for bomb ingredients and that the mention of a wedding hinted at a planned attack.
Lawyers for the men said the emails were innocent and the security services' interpretation of the emails was "far-fetched".