Zambia's election commission has postponed the announcement of partial results from a presidential vote after complaints from the opposition, whose supporters clashed with police outside the counting center in the capital, Lusaka.

Election commission chief Ireen Mambilima said Wednesday that officials will resume announcing results starting on Thursday morning.

Opposition leader and presidential candidate Hakainde Hichilema has noted that some polling stations were staying open Wednesday, a day after the election. He says announcing results while voting is still underway would undermine the process.

Police at the counting center in Lusaka fired tear gas to disperse some activists from the opposition United Party for National Development who had camped outside the building.

The election was held to replace Michael Sata, who died in October after a long illness.