Ghana's ruling party said on Tuesday that President Nana Akufo-Addo held a slight lead in his bid for re-election over his main rival John Mahama, according to its preliminary tally based on results from nearly nine out of ten polling stations.

The election on Monday was considered a two-horse race between the incumbent Akufo-Addo and his predecessor Mahama, who offered competing plans to end an economic crisis in West Africa's second-largest economy.

Ghana emerged last year from a three-year lending programme with the International Monetary Fund only for the pandemic to knock demand for its key exports of oil and cocoa, leading to the economy's first quarterly contraction in nearly 40 years.

Akufo-Addo secured more than six million votes from 88% of polling stations nationwide, representing a 52.72% share of ballots counted, said John Boadu, general secretary of the president's New Patriotic Party (NPP).

"We will refrain from declaring results ... However, this puts the NPP candidate, Nana Addo Dankwa Akufo-Addo, in the lead," Boadu told reporters.

He said the NPP was also confident of maintaining a majority in parliament. The election commission is expected to declare certified results from the presidential and parliamentary elections later on Tuesday.

Mahama's campaign team did not immediately respond to a request for comment but said overnight that the NDC had flipped dozens of parliamentary seats. Boadu rejected the claims.

The parties have alternated in power since 1992 and this was the third straight election in which Akufo-Addo and Mahama have faced off.

The vote was peaceful, consistent with Ghana's reputation as one of West Africa's most stable democracies.

The two sides had agreed last week to resolve any disputes in court after fears that unofficial security groups hired by politicians could disrupt the vote.