Zimbabwe president Robert Mugabe, 90, fell down steps from a podium after speaking to supporters upon his return from Ethiopia.
Mugabe appeared to miss a step and toppled when he left the raised lectern at the airport, according to several witnesses.
His aides quickly helped him up and escorted him to his limousine which sped away, they said.
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 January 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 check-ups on his eyes, according to Zimbabwean officials.
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 US 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.