Zambian police have fired tear-gas to disperse about 100 supporters of the leading opposition candidate in the presidential election.

A number of Hakainde Hichilema's United Party for National Development supporters waiting for results of the closely fought race were arrested and forced into a police van on Wednesday, an AFP news agency reporter said.

The group had kept a vigil outside a conference centre in Lusaka where the first batch of official results from Tuesday's vote were expected to be released.

Al Jazeera's Haru Mutasa, reporting the scene of the confrontation in the capital Lusaka, posted this tweet:  

The electoral commission suspended the announcement of the results after extending the vote for a day because heavy rains had prevented polling officials from reaching some remote areas.

Police initially asked the supporters to disperse but one of them shouted back at the officers, who then drove them off with batons and tear-gas.

It is a traditional practice for supporters of a party that thinks it is winning an election in Zambia to gather outside the results venue to wait for the announcement.

In several previous cases party supporters have also been forcibly removed with the use of tear-gas.

Hichilema is seen as the main challenger to ruling Patriotic Front party candidate Edgar Lungu, in the contest to win the presidency after the death in office of Michael Sata last October.

Source: Al Jazeera and agencies