Soldiers have been deployed in Malawi's commercial capital Blantyre after voters, angered by delays and mishaps at polling stations in the hotly contested presidential election, torched voting materials and blocked roads.

Polling stations had opened as much as 10 hours late on Tuesday, sparking anger and speculation about the fairness of the vote.

Some polling stations did not have enough ballot papers and ink.

"We come here at 4 in the morning to vote. Up to 9am there is no voting. There is no ink to vote," a voter told Al Jazeera.

At another polling station in Blantyre, a crowd torched election materials when they arrived hours late and in other constituencies they blocked roads with rocks before the military arrived to back up police, Reuters news agency reported.

In the city centre angry youths staged an impromptu mini-protest chanting anti-government slogans.

Voting extended

Voting was extended for several hours in some locations, and the electoral commission said voting would continue on Wednesday at polling stations where balloting was disrupted.

Election chief Maxon Mbendera acknowledged an "embarrassing situation" with the organisational hiccups.

"Defence Force personnel will deploy to strengthen the presence and security already being provided by the Malawi Police Service," the AFP news agency quoted him as saying.

Thirteen polling stations, far less than one percent of the more than 4,000 voting centres around the country, "where polling papers were destroyed or there were serious disruptions of the polling process" will re-open on Wednesday, he said.

Some challengers of incumbent President Joyce Banda, southern Africa's first female head of state, had already cried foul in the election run-up, saying they had unearthed plots to skew the ballot.

Opinion polls indicate the presidential poll is too close to call, but many analysts rank People's Party leader Banda as favourite because of her popularity in rural areas where she has been rolling out development projects and farm subsidies.

After casting her ballot in the southern village of Malemia, Banda urged all sides to keep calm.

"I'm thankful that the campaign period was peaceful and am urging all Malawians to vote peacefully today without any incident or loss of life," she told reporters.

Corruption scandal

Banda came to power in the landlocked, impoverished nation two years ago after the death of her predecessor, Bingu wa Mutharika.

She initially enjoyed huge goodwill from the many who disliked Mutharika's autocratic style, and won the backing of foreign donors and the International Monetary Fund when she pushed through austerity measures, including a sharp devaluation of the kwacha, to stabilise the farming-dependent economy.

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However, more recently her administration's reputation has been hit by a $15m graft scandal, dubbed "Cashgate" after the discovery of large amounts of money in the car of a senior government official.

More than 80 people have been arrested and a former cabinet minister has been dismissed and put on trial for money laundering and attempted murder.

Urban voters have criticised Banda's response as ponderous and relations with donors have soured.

Banda's main challenger is Lazarus Chakwera, an evangelical pastor who retired from the church last year to lead the Malawi Congress Party.

Mutharika's younger brother Peter is also running as the head of the Democratic Progressive Party.