Baghdad  - The US military said Tuesday 21 suspected members of the al-Qaeda in Iraq militant group were captured during operations in northern Iraq a day after Iraqi troops held six teenagers who they said were being trained against their will to carry out suicide bombings.

US troops captured a man believed to be responsible for constructing car bombs during an operation Tuesday in the north-west of Baghdad, a US military statement said.

The man belongs to a terror cell, which was allegedly behind a May 16 car bombing in Fallujah that left four Iraqi policemen dead, the statement said.

Suspected members of al-Qaeda were also held in separate operations in the northern city of Mosul and Baghdad.

The arrests come a day after the Iraqi Interior Ministry announced that its troops rounded up six teenagers in Mosul, who were being trained against their own will to carry out suicide bombings.

House searches in Mosul, the hotbed of Sunni extremist insurgents, led to the arrest of six boys between the ages of 15 and 18, who were being trained to carry out suicide attacks against troops, according to the ministry.

Al-Qaeda insurgents forced the boys into compliance by threatening to kill them or their families, Deputy Interior Minister Kamal Ali Hussein told reporters.

Iraqi troops backed by the US military are launching a major crackdown, codenamed the Mother of Two Springs, targeting al-Qaeda insurgents in Mosul, the capital of Nineveh province.

Separately, leaders of local tribal police, known as the Awakening Councils, told the pan-Arab daily al-Hayat that a terror group "the Youths of Heaven" extended its area of operations to northern Baghdad.

The group linked to al-Qaeda targets mainly members of the Awakening Councils, General Said Aziz Salman, the head of the Taji council, told al-Hayat.

Most members of the Youths of Heaven group are children and youths, Salman said adding that they extended their operations to Baghdad's northern districts.

The group has been operating in Baghdad's western district of Amiriyah, Salman said. (dpa)