Macedonia's parliamentary election was marred by violence in Albanian areas and suspected fraud on Sunday, with one person shot dead and nine wounded, and voting halted in one town after a gun battle.
The poll is seen as a test of the nation's political maturity after campaign violence raised fears that slow progress toward European Union membership could be further delayed.
Police arrested a former leader of an ethnic Albanian guerrilla group in connection with the violence, a senior government source said.
The country's electoral commission said there were instances of suspected fraud and irregularities such as broken or missing ballot boxes and stolen voting materials.
"I have to express my regret and worry that after the elections in 2006, which were overall evaluated as very good, this year we have bad elections, with a great number of incidents," commission chief Jovan Josifovski told reporters.
Scuffles broke out in several Albanian areas and a small explosive device was thrown at an empty cafe. Near Skopje, voting was stopped in the town of Aracinovo after a gun battle.
Police said officers went to the town after local monitors reported the arrival of men with machine guns. They came under fire and retaliated, killing one gunman and injuring two others.
The ethnic Albanian Democratic Union for Integration (DUI) said the incident was initiated by plain-clothes police.
"They stopped our convoy and shot one round in the air, it was chaos, we got out from the cars and tried to flee," DUI official Shefik Duraku told Reuters.
Several police vehicles, including armoured personnel carriers, were stationed just outside Aracinovo. The way into town was blocked by cars parked in the middle of the street.
In Skopje's Cair neighbourhood, another shooting took place in the courtyard of a school serving as a polling station.
One DUI official was in critical condition and five other people were wounded, police said.
At least people have been arrested in connection with the violence. They included Agim Krasniqi, a commander of the Albanian National Army in a 2001 rebellion who remained active after a peace deal was reached.
The DUI's leader, former guerrilla commander Ali Ahmeti, blamed the rival Democratic Party of Albanians (DPA) and the police for "provocations, violence and psychological terror".
"What happened today is a black mark on Macedonia," he said.
The two parties are bitter rivals for the vote of the 25-per cent Albanian minority. They have been on bad terms since 2006, when the DUI, which won most of the Albanian votes, was left out of a coalition government in favour of the DPA.
The violence is the worst since the end of the 2001 rebellion, when all-out ethnic war was averted by the West using the lure of NATO and the EU to secure more rights for Albanians and get guerrillas to disarm.
"The situation in the country overall is stable," Prime Minister Nikola Gruevski told reporters. "The incidents are small in number and mostly in ethnic Albanian areas. There will certainly be a repeat vote in those areas in two weeks."
Gruevski's conservative VMRO-DPMNE party is expected to win the vote on a surge of nationalist defiance after Greece blocked Macedonia's Nato bid in April in a 17-year row over the name it shares with a Greek province.
Gruevski's government, which will likely have to include a partner from the ethnic Albanian parties, will be asked to get Nato accession back on track, start EU membership talks and calm tensions after weeks of violence among rival Albanian factions.
Brussels has made clear the election is a test Macedonia must pass to start EU negotiations.
Serhiy Holovaty, head of the Council of Europe monitoring mission, told Reuters he had seen some irregularities in his early morning visits to a few polling stations, and had "noticed the possibility of manipulation of the results".
Some 1.77 million people are entitled to vote. Polls close at 7 pm (1700 GMT), with voting overseen by an estimated 6,000 local and foreign monitors.