The head of the United Nations cultural body vowed in Baghdad Saturday to step up measures aimed at protecting Iraq's heritage, which has been systematically targeted by jihadist militants.

UNESCO chief Irina Bokova launched a Japanese-funded initiative to preserve Iraq's museum collections and threatened heritage, as well as a social media campaign under the hashtag #Unite4Heritage.

"Today our pledge is we will never relent in safeguarding the great cultural heritage and diversity of Iraq," she said, speaking from the recently reopened national museum in Baghdad.

Heritage experts have admitted that little could be done to save sites in areas controlled by the Islamic State jihadist group.

In February this year, IS militants smashed priceless artefacts at the museum in Mosul, which is Iraq's second city and the jihadist group's main hub.

They are also believed to have looted and destroyed artefacts at archaeological sites including at the ancient city of Hatra, which is listed as a world heritage site by UNESCO.

Bokova said, however, that the agency would reinforce "protection tools, including inventories and the use of remote sensing and satellite imaging" to monitor the country's heritage.

She cited UNESCO successes such as saving Abu Simbel from rising Nile waters in the sixties or rebuilding the Mostar bridge in Bosnia and Herzegovina in 2004.

The jihadists claim statues are idolatrous, but experts point out that IS has mainly destroyed the objects that were too bulky to smuggle out and sell.