BUCHENWALD, Germany (Reuters) - U.S. President Barack Obama took aim at those who deny the Holocaust -- including Iran President Mahmoud Ahmadinejad -- when he made an emotional visit to the Buchenwald concentration camp on Friday.

After telling a U.S. television network that Ahmadinejad should visit Buchenwald himself, Obama accompanied two survivors of the Holocaust and Chancellor Angela Merkel on a tour of the camp, outside Weimar in eastern Germany.

Obama walked through an open space where prisoner barracks had stood and past a crematorium with eight ovens before placing a white rose on the site where survivors erected a temporary monument for Buchenwald’s liberation in April 1945.

“To this day we know there are those who insist the Holocaust never happened, a denial of a fact or truth that is baseless, ignorant and hateful,” Obama said in a brief address.

“This place is the ultimate rebuke to such thoughts, a reminder of our duty to confront those who would tell lies about our history,” he added. “I will not forget what I have seen here today. These sights have not lost their horror over time.”

Obama, whose great uncle was among the first Americans to enter a Nazi concentration camp in the closing months of World War Two, did not mention Ahmadinejad at the camp itself.

But earlier, Obama told NBC News that Ahmadinejad, who called the Holocaust a “great deception” this week, should visit the site himself. “I have no patience for people who would deny history.”

The symbolic visit sent a message that Israel is still a priority for U.S. foreign policy in the Middle East after Obama made a major speech addressed to Muslims in Cairo on Thursday.

Obama has offered Iran a new beginning in diplomatic engagement, but Iran’s Supreme Leader Ayatollah Ali Khamenei has urged voters in next week’s presidential election to support anti-Western candidates.

Obama recalled his great uncle Charlie Payne, who as a young U.S. soldier helped liberate one of Buchenwald’s 130 sub camps.

“I’ve known about this place since I was a boy, hearing stories about my great uncle,” Obama said.

“He returned from service in a state of shock, saying little and isolating himself for months on end from family and friends along with the painful memories that would not leave his head.”

Buchenwald survivor and Nobel laureate Elie Wiesel, 80, accompanied Obama to the camp set up by the Nazis in 1937. An estimated 56,000 people were killed there.

Obama and Merkel also visited the so-called Little Camp, where the conditions and treatment of prisoners were especially poor. Wiesel was kept there for some time. Little Camp was known as the Jewish Camp because nearly all of its about 2,000 prisoners were Jews -- Polish, French, Russian and Dutch.

The camp’s gatehouse is intact and the words “Jedem das Seine” (“To each his destiny”) are carved into the iron gates.