Insurgents have tunnelled into the main jail in Afghanistan's volatile Kandahar province freeing hundreds of prisoners, including many Taliban commanders.
The escape is seen as a serious setback for United States forces who hope to start withdrawing in coming months.
Kandahar's governor says 476 prisoners managed to escape due to the "negligence" of Afghan security forces.
The prison, supposed to be one of the country's most secure, sits on the outskirts of Kandahar city and holds captured insurgents and criminal prisoners, Reuters reports.
The Taliban says the 360-metre-long tunnel took months to construct.
The jailbreak comes months before the start of a transfer of security responsibilities from foreign to Afghan forces in several areas as part of the eventual withdrawal of coalition forces from the country.
It is the second major escape in three years at the prison. In 2008, about 1000 prisoners, including Taliban militants, escaped after a truck bomb was used to blow open the gates.
Kandahar is seen as the birthplace of the movement and the city and surrounding area bas been the scene of some of the worst fighting in Afghanistan.