A demolished vehicle sits in front of the prison gate after Taliban militants attacked and freed 1,000 prisoners, including about 400 Taliban militants. (Allauddin Khan/Associated Press)

NATO leaders acknowledged that Taliban militants scored a success in Afghanistan Friday with a daring attack that freed 400 of their number and 600 common criminals from a Kandahar jail, but insisted it would not change NATO's resolve.

They remained optimistic, even though only six of the 1,000 prisoners had been recaptured by Saturday night.

"The operation was a success for the Taliban. We must admit that," but NATO will continue to take initiatives against the militants, said Brig-Gen. Carlos Branco, a spokesman for NATO forces in Afghanistan.

"Typically you have good days and bad days," said Gen. Denis Thompson, the Canadian commandeer in Afghanistan. "Clearly, yesterday was a bad day."

Gen. Rick Hillier, chief of Canada's defence staff, said the attack wouldn't hurt morale. "It doesn't indicate a massive breakdown whatsoever. These things do occur."

But one Afghan was not so optimistic, saying it revealed the weakness of the government. One resident of Kandahar told CBC News he's keeping family members inside because they're terrified of the escapees, and tension in the city is high.

Canadian soldiers were hoping to provide intelligence about the whereabouts of the missing Afghans to government soldiers, as U.S. marines searched for the missing men door to door in Kandahar.

The Taliban launched a co-ordinated assault on Sarposa Prison, destroying its front gate. Prisoners — who may have been tipped about the attack and were ready to flee — rushed out, Afghan officials said.

When the sun rose over the city Saturday, twisted metal, rubble and overturned vehicles were everywhere.

During the assault, a truck bomb went off at the main gate. A second bomb was detonated simultaneously, destroying a nearby police substation and killing nine officers, interior ministry spokesman Zemeri Bashary said.

Rockets demolished an upper prison floor.

A Taliban spokesman, Qari Yousef Ahmadi, said 30 insurgents on motorbikes and two suicide bombers attacked the prison.

It's believed about 400 Taliban fighters are among the escapees.

There were no indications that the militants received help from the inside, but as a precaution the prison's chief official, Abdul Qabir, was placed under investigation for possible involvement, said Mohammad Qasim Hashimzai, a deputy minister at the justice ministry.