BAGHDAD, Iraq — Before he quit as head of Iraq’s antiquities board, Donny George made a final desperate attempt this summer to safeguard the relics of 5,000 years of history: He ordered the doors of the National Museum plugged with concrete against the near-unbridled looting of ancient artifacts.

The longtime guardian of Iraqi antiquities under Saddam Hussein and later under a government led by Shiite religious parties, Mr. George then left the country and sent in notice of his resignation in early August, Culture Ministry officials confirmed Saturday.

Mr. George, who first alerted the world to the looting of Iraq’s irreplaceable ancient works of art and writings in the first days after American troops moved into Baghdad in 2003, told the Art Newspaper that he found “intolerable” the ongoing failure of Iraqi leaders and the American military to protect the sites. On Saturday, the London-based monthly became the first to report Mr. George’s departure.

Mr. George, an Iraqi Christian, cited what he said was growing pressure by officials of Iraq’s ruling Shiite parties to emphasize Iraq’s Islamic heritage and ignore the earlier civilizations that stretched back to Babylon and beyond. “A lot of people have been sent to our institutions,” the Art Newspaper quoted him as saying. “They are only interested in Islamic sites and not Iraq’s earlier heritage.”

Mr. George also complained of a lack of funding to protect archaeological sites around Iraq. Funding runs out in September for 1,400 specially trained patrolmen who guard archaeological sites, he told the art publication, and no more money has been budgeted to protect places that date back to the Sumerian civilization in the year 3000 before the common era.

“I can tell you the situation regarding antiquities is horrible,” an authority on Mesopotamian archaeology at the Oriental Institute at the University of Chicago, McGuire Gibson, said by telephone.

“There was a lot of attention paid to the looting of the museum the very same days the war started,” Mr. Gibson said. “It hasn’t stopped. There has been looting of sites on an industrial scale. Some of the greatest Sumerian sites have gone.”

In the weeks before the American-led invasion, Mr. Gibson worked to alert the American military to the thousands of ancient sites across Iraq. The work helped save Iraq’s heritage from American bombs but not from the looting — unforeseen by American military and civilian war planners — that broke out after the collapse of Saddam’s government. Mobs ransacked government buildings down to the light switchplates and often set fire to them afterward, over days of chaos in Baghdad and other cities. American troops, with no orders to stop the looters, watched for several days before moving against the thieves.

At the time of the invasion, the National Museum contained at least 170,000 items, some of which were moved elsewhere for safekeeping just before the outbreak of hostilities. In those first days after American troops entered Baghdad on April 9, at least 13,000 pieces from the museum were believed to be stolen.

“It was the leading collection … of a continuous history of mankind,” Mr. George said on April 13, 2003, as he crunched through glass from shattered display cases and ransacked museum offices. “And it’s gone, and it’s lost.”

The Culture Ministry ordered the museum closed and has not announced plans to reopen it. It now sits surrounded by weeds behind metal gates, piled sandbags, and concertina wire. Wary guards came to a front gate holding pistols and Kalashnikov assault rifles Saturday and confirmed that the museum’s front entrance had been sealed.

Mr. George said he acted on his own when he ordered the doors sealed this summer after government officials did not immediately respond to his request for permission. “It was the only way to guarantee the museum’s safety,” Mr. George told the Art Newspaper. Colleagues say he has moved with his family to Syria.

Mr. George did not immediately respond to a request by e-mail late Saturday for comment. The culture minister, a Sunni Muslim, could not be reached for comment on Saturday, which is not a government work day in Iraq.

Culture Ministry officials, speaking on condition of anonymity because they said they were not authorized to comment, confirmed that Haider Farhan, a member of a Shiite religious party, has become the acting head of the State Board of Antiquities and Heritage since Mr. George’s departure. Mr. George told the Art Newspaper that Mr. Farhan had no relevant experience for the job; a Culture Ministry official questioned that judgment, saying Mr. Farhan was a young official in the department with a master’s degree in Islamic manuscripts.

“If they are now going to be projecting an Islamic line, let them do it,” Mr. Gibson said from Chicago. “They shouldn’t be damaging pre-Islamic ones in that effort.”

“The destruction that’s already gone on in looting since 2003 is irrevocable,” he said. “We’ve lost whole sites. We’ve lost whole cities.”