Ghana's ruling party held a one-seat lead in parliament with one race still to be decided, the election commission said on Thursday, as the main opposition leader rejected the outcome and called for a full audit of results.

President Nana Akufo-Addo was awarded a second four-year term in office in Monday's election, following a tightly contested vote that was tainted by violence in which five people died.

Akufo-Addo's New Patriotic Party (NPP) lost dozens of seats but retained 137, while that of his predecessor and old rival John Mahama, the National Democratic Congress (NDC), secured 136, according to the commission. Mahama said his party won the undeclared seat. Another was won by an independent.

The loss of his clear majority may make it harder for Akufo-Addo to implement his agenda, including a promised $17-billion programme to boost growth in one of West Africa's largest economies.

The NPP has alternated in power with the NDC since 1992, giving Ghana a reputation as a robust democracy in an unstable region where election disputes this year have prompted fears of a democratic backslide.

Mahama accused the election commission of manipulating results in favour of his opponent and said his party had won both the presidential and parliamentary elections.

Mahama spoke to his supporters about several issues including that the "aggregates on the summary sheets in some constituencies do not reflect on the polling station pink sheets."

The election commission has not yet agreed to a "full forensic audit" as requested by Mahama and was not immediately available for comment.

A European Union observer mission said the vote was well organised but noted several problems including numerous instances of vote-buying that resulted in an unlevel playing field.

The coronavirus pandemic hit the price of oil and cocoa exports this year, resulting in the first quarterly contraction in nearly 40 years for Ghana, one of Africa's largest gold producers.