LAHORE - Five American youths arrested for trying to link up with Islamist militant groups were remanded in custody for another 10 days by a Pakistani court on Tuesday, police said.

The men were detained in Pakistan last week on suspicion of trying to contact Al-Qaeda-linked organisations and engage in militant activities, possibly in the lawless northwest where the Taliban insurgency is fiercest.

"Police produced the five men before the court in Sargodha and obtained their 10-day physical remand for further questioning," senior police official Tahir Gujjar told AFP.

The men, who are all US citizens with dual nationality including two Pakistani-Americans, have been questioned by the FBI and Pakistani officials since their arrest last week in the eastern town of Sargodha.

A court in the main eastern city of Lahore on Monday blocked the immediate deportation of the five to the United States or any possible handover into FBI custody.

"Initial investigation reveals that these men have links with jihadis," a senior security official told AFP on condition of anonymity.

He said police had found some of their belongings during a raid on Monday on a hotel in the southern city of Karachi where they stayed before moving to Sargodha.

"This material will greatly help in the investigation process," the official said without elaborating.

An official close to the investigation told AFP on Saturday that the men, who left the United States last month, had contacted a man with links to Al-Qaeda and sought to go to the tribal region of Waziristan for training with extremist groups.

The arrests have raised fears that Muslim radicalisation is gaining momentum in the United States, creating high-value recruits for Islamist groups, and US President Barack Obama has vowed an investigation.