BAGHDAD (AP) - Iraqi forces pressed their offensive against the Islamic State group Friday, expecting to reach the outskirts of the militant-held city of Tikrit, a day after the extremists reportedly “bulldozed” a famed archaeological site in the area.

In Paris, the head of the U.N.'s cultural agency said the deliberate destruction of cultural heritage _ such as the latest rampage at Iraq's archaeological site of Nimrud _ amounts to a “war crime.''

The discovery of the treasures of Nimrud's royal tombs in the 1980s is considered one of the 20th century's most significant archaeological finds. It dates back almost 3,000 years and has been compared to King Tutankhamun's tomb in Egypt.

The battle to wrest Tikrit _ Saddam Hussein's hometown _ from the Islamic State is a major test for the Iraqi forces and allied Shiite militias fighting on their side.

The governor of Salahuddin, Raed al-Jabouri, said that Iraqi forces expect to reach Tikrit later Friday. He told The Associated Press they still have not made it to Tikrit's east airport as some reports have suggested.

Tikrit, 130 kilometers (80 miles) north of Baghdad, has been under the control of the Islamic State group since June, when the Sunni militants made a lightning advance across northern Iraq, prompting Iraqi troops to flee and abandon their weapons.

On Monday, Iraqi security forces launched a large-scale operation in an effort to retake the city from the militant group, but the offensive was stalled somewhat, with military officials saying the militants strategically lined roads leading to the city with explosives and land mines.

Meanwhile, the Iraqi Ministry of Tourism and Antiquities said late Thursday that the IS militants “bulldozed'' the renowned archaeological site of the ancient city of Nimrud in northern Iraq.

The destruction is part of the group's campaign to enforce its violent interpretation of Islamic law, destroying ancient archaeological sites it says promoted apostasy.

The ministry's report could not be immediately independently confirmed.

In Paris, UNESCO chief Irina Bokova appealed in a statement Friday to people around the world _ “especially youth'' _ to protect ``the heritage of the whole of humanity.''

Bokova denounced "this cultural chaos'' and said she had alerted both U.N. Secretary-General Ban Ki-moon and the prosecutor of the International Criminal Court.