A lack of forces has delayed the start of what Iraqi Prime Minister Nuri al-Maliki has vowed will be a "decisive battle" against Al-Qaeda in the war-torn city of Mosul, an official said on Thursday.

The operation, which two weeks ago officials said would start within "days" is now only likely to be launched in the coming weeks, said Khorso Korane, deputy governor of northern Nineveh province of which Mosul is the capital.

"The delay in the start of the military operation in Mosul is because of a lack of troops," Korane told AFP.

"Since the prime minister came to Mosul (on February 2), Iraqi troops have been preparing the security operation but we still don't have enough troops. It is possible that in the next weeks we will start our operation," he said.

"When the security plan starts it will reach the Syrian border."

However Korane also said that US and Iraqi forces are conducting "ongoing operations."

"We are striking the terrorists' strongholds and have already limited and paralysed their movements."

Residents of Mosul, 370 kilometres (230 miles) north of Baghdad, have been stocking up with supplies in anticipation of the battle, traders say.

Maliki on January 25 promised a "final war" against Al-Qaeda in the city, considered by the US military to be the last urban bastion of the Iraqi branch of Osama bin Laden's jihadist network.

Two days earlier, a cache of munitions stored by insurgents blew up in a building in west Mosul's Zanjili suburb, killing up to 60 people according to the Iraqi Red Crescent.

A suicide bomber killed provincial police chief Brigadier General Salah al-Juburi and two other officers the next day when they went to inspect the carnage.