Zambia's electoral commission has suspended the counting of votes from Thursday's presidential, parliamentary and local elections over alleged attacks on polling staff.
The authority said the process would be halted nationwide with immediate effect as it expressed concern over reports of violence that had "resulted in the theft of marked ballot papers in ballot boxes".
President Hakainde Hichilema is seeking a second five-year term. Brian Mundubile is the main opposition candidate among 13 challengers.
The electoral commission had previously set itself the target of announcing the results by the end of Sunday.
Counting got under way immediately after polls closed on Thursday but no official results had been declared when the halt in the count came into effect.
In Friday's statement, the commission said it would review the decision to suspend vote counting within the next 24 hours.
Just hours before the commission's statement, Mundubile expressed "grave concern" over delays in the announcement of presidential results, warning that the delay could create opportunities for interference or manipulation.
He cited what he described as "deeply troubling reports" from several areas, including alleged military involvement at totalling centres and allegations concerning the movement of ballot boxes.
He called for the immediate publication of results polling station by polling station, protection of the chain of custody and investigations into the reported incidents.
Hichilema also issued a statement urging Zambians to "remain peaceful, patient and patriotic as we await the official outcome from those entrusted with managing the vote".
Polling day was largely peaceful, with queues reported in many areas and only isolated delays. Along with electing a president and MPs, the more than eight million registered voters had the chance to choose a new parliament and local councils.
Thursday's vote was seen as a test of Zambia's reputation as one of Africa's most stable democracies, amid concerns that political freedoms are being undermined.
Despite 14 candidates being on the presidential ballot paper, the contest was largely seen as a two-horse race between the incumbent and his main challenger, Mundubile - running on the banner of the National Reconciliation Party for Unity and Prosperity (NRPUP).
Hichilema is credited with steering Zambia through a difficult economic climate but his popularity was dented as many people said their circumstances have not improved. Mundubile hoped to capitalise on that dissatisfaction.
Mundubile is a former minister in the Patriotic Front (PF) government that ruled from 2011 to 2021, with his alliance drawing support from backers of the late former President Edgar Lungu.
Hichilema, 64, won the 2021 election on his sixth attempt and is betting on job creation and an ambitious infrastructure drive to secure a second and final term.
The election was seen as a referendum on his economic record, which has boasted debt restructuring, currency strengthening and lowered inflation.