Zambia's main opposition party says President Rupiah Banda is ineligible for re-election because both his parents were allegedly born outside the country.
The Patriotic Front says Banda's father was born in colonial-era Nyasaland - modern-day Malawi - and says it took out an injunction on Thursday to prohibit Banda from running in September's election. Zambia's constitution requires presidential candidates to have Zambian-born parents.
The ruling Movement for Multi-Party Democracy dismissed the challenge, questioning why the opposition had not raised the issue during the last election.
Banda, the former vice president, narrowly won a 2008 presidential poll forced by the death of president Levy Mwanawasa. Banda, who is in his 70s, was born before Zambia gained independence in 1964.