BAGHDAD (AFP) - Iraq's national museum officially reopened Saturday after 12 years of painstaking efforts during which close to a third of 15,000 stolen pieces were recovered.

The much-delayed reopening was brought forward in what officials said was a response to the destruction of priceless artefacts by Islamic State in Iraq and Syria (ISIS) in the northern city of Mosul.

"We have been preparing to reopen for the past couple of months, the museum should be open to everyone," Deputy Tourism and Antiquities Minister Qais Hussein Rashid told AFP.

"The events in Mosul led us to speed up our work and we wanted to open it today as a response to what the gangs of Daesh did," he said, using an Arabic acronym for ISIS.

On Thursday, the extremists who have occupied Iraq's second city of Mosul since June last year released a video in which militants smash ancient statues with sledgehammers.

Militants are also seen defacing a colossal Assyrian winged bull in an archaeological park in Mosul with a jackhammer.

The destruction sparked global outrage, calls for an emergency meeting of the UN Security Council and fears over the fate of other major heritage sites in areas under ISIS control.

The Mosul destruction was the worst disaster to strike Iraq's treasure since the national museum in Baghdad was looted in the chaos that followed the US-led toppling of Saddam Hussein.