Electoral papers burning outside a polling station in Lusaka, Zambia.
Angry voters allegedly torched the material after the polling station failed to open on time.
A police chief blamed the disruption on trouble-makers.
(SOUNDBITE) (English) MULAKENI ZULU, LUSAKA COMMANDING OFFICER:
"This confusion is not by the electorates there. It's just from an unknown group from outside who started throwing stones inside there just to disrupt the peaceful voting process."
Zambians are voting in a closely contested election between incumbent Rupiah Banda, and opposition leader Michael Sata - a vocal critic of foreign investment in Africa's biggest copper producer.
Sata was mobbed by frustrated youths at the polling station.
Security across the country has been stepped up for the election, although political violence in Zambia is uncommon.
Earlier in the day, people had queued for hours for their chance to vote.
(SOUNDBITE) (English) JONATHAN MTONGA, LUSAKA RESIDENT:
"This has been the most eagerly awaited election, very important, shaping our future, making sure we put the right people in power."
(SOUNDBITE) (English) EMILY SIKAZWE, LUSAKA RESIDENT:
"It is an important civic duty to choose your leader that can represent you according to your hopes and aspirations."
An opinion poll published a week ago suggested Banda held a narrow lead over Sata, although the number of undecided voters means an upset is still possible.
Nick Rowlands, Reuters.