An aide to Abu Mussab al-Zarqawi, a Jordanian-born terror master in Iraq, has been arrested in the northern city of Mosul, a senior spokesman for the Iraqi government said Thursday.

Qassim Dawood, the national security advisor, identified the detainee as Abu Saeed, but gave no further details.

Iraqi and US officials have believed that Zarqawi, purportedly al-Qaida's top leader in Iraq, had fled Fallujah, 50 km west of Baghdad, ahead of the massive offensive on the city.

Mosul, 400 km north of Baghdad, has become a scene of an upsurge in attacks, kidnappings and assassinations in the last weeks.

Zarqawi's group has declared on a website that it executed two Iraqi National Guards in front of a large crowd of people in broad daylight in Mosul.

It has claimed responsibility for many of the deadliest suicide bombings in Iraq since the fall of Saddam Hussein and has beheaded several foreign hostages.

The US administration has offered a 25 million US dollars bounty for information leading to his death or capture.