A senior Zambian government official has said that some political parties were asking prospective female candidates for sexual favours in exchange for selection ahead of August's general election.

"I am going to appeal to all female aspiring candidates to ensure that they record all these cases," Mainga Kabika, the civil service head of the gender office in the presidency, said on Monday.

She did not name the political parties involved.

Zambia has a big gender imbalance in national politics with around 15% of MPs being women. Their under-representation at leadership level reflects "deep-rooted cultural and structural barriers", a statement from the president's office said last year.

Kabika was addressing a conference of state prosecutors when she revealed that women had been in touch with her about what they were being asked to do.