President Robert Mugabe, 90, fell down steps from a podium after speaking to supporters upon his return from Ethiopia, say witnesses.

Mugabe appeared to miss a step and toppled when he left the raised lectern at the airport Wednesday afternoon, according to several witnesses, who insisted on anonymity because of security concerns.

His aides quickly helped him up and escorted him to his limousine which sped away, they said.

"He addressed supporters who welcomed him ... He missed a step as he walked down from the podium and immediately fell down," said a witness.

Some press photographers who captured the fall said they were forced to delete their pictures by security personnel.

Mugabe's spokesman was not immediately available for comment.

Mugabe was elected chairman of the 54-nation African Union at a summit of African leaders on Jan. 30 in Addis Ababa, Ethiopia. The role of rotating AU chairman is largely ceremonial.

He celebrates his 91st birthday on February 21. Mugabe takes annual vacations every January to Asia, including Singapore where he has visited specialists for checkups on his eyes, according to Zimbabwean officials. The Zimbabwean leader has repeatedly insisted that he is "fit as two fiddles."

Zimbabwe, a once-prosperous nation of 13 million people in southern Africa, has struggled since Mugabe's government began seizing white-owned farms in 2000. Mugabe is accused of using widespread violence to win several disputed elections, according to human rights groups. The country suffered hyperinflation until it abandoned its currency for the U.S. dollar in 2009.

The EU imposed sanctions on Zimbabwe in 2002 over abuses linked to national elections, banning travel in Europe and freezing the assets of dozens of officials and business representatives. The measures have been gradually lifted in recent years to encourage reform but Mugabe and his wife Grace remain on the EU blacklist.

Now that Mugabe is the head of the African Union, the European Union has decided to ease its travel ban on him while he is chairman for the next year.