Insurgents fired a mortar at a ceremony attended by top U.S. officials on Tuesday to hand over a presidential palace in Saddam Hussein's hometown to local Iraqi authorities, sending the U.S. ambassador scrambling for cover but causing no injuries.

As a U.S. colonel was giving a speech, the mortar round fell about 300 yards from the palace in Tikrit, 80 miles north of Baghdad.

The U.S. ambassador to Iraq, Zalmay Khalilzad, and the U.S. commander in Iraq, Gen. George Casey, briefly went inside the palace following the blast, but emerged a few minutes later to continue the ceremony.

Afterward, they took a tour through the building, which Saddam ordered built for his mother in 1991 and is considered the largest and most elaborate of the palaces built during his rule.

The palace is part of a complex on more than 1,000 acres overlooking the Tigris River. There are 136 buildings on the property, with a combined 1.5 million square feet of administrative and living space, including 18 palaces, the U.S. command said in a statement before the ceremony.

"The planned turnover of the complex to the Iraqi Ministry of Finance and the provincial government will be a landmark event highlighting the increased capability of the Iraqi government to administer and govern itself," Col. Billy J. Buckner, Multi-National Corps-Iraq spokesman, said in the statement.

Since it was taken over by U.S. troops in 2003, it has served as a division headquarters for U.S. forces based in the region.

"Although 28 other coalition operating bases have already been turned over to Iraqi Security Forces control this year, the Tikrit Palace complex is the most significant transition of real estate thus far," the U.S. statement said.