Violence and allegations of rigging meant Macedonia's election on Sunday fell short of international standards, foreign observers say.
At least one person was killed in gun fights that broke out in ethnic Albanian areas.
The fighting cast a shadow over the vote, in which Prime Minister Nikola Gruevski won a convincing victory.
Correspondents say the violence and poll disruptions may have undermined Macedonia's EU and Nato aspirations.
Election officials said with nearly all the votes counted, the prime minister's VMRO-DPMNE party had about 47% - more than twice the support for the Social Democrats, who had taken 23%.
It appeared this would be enough to give the party a parliamentary majority, without relying on other parties for coalition support.
'No free vote'
However, observers said they could not give the poll a clean bill of health.
"Key international standards were not met," said monitors for the Organisation for Security and Cooperation in Europe (OSCE).
"Organised attempts to violently disrupt the electoral process in parts of the ethnic Albanian areas made it impossible for voters... to freely express their will."
In the Albanian stronghold of Aracinovo at least one person was killed and more than 20 were arrested following shootings between rival parties or with the police, and election officials closed a number of polling stations amid reports of intimidation and fraud.
Ethnic Albanian rebels fought an insurgency in 2001, demanding more rights for their community, which makes up about a quarter of Macedonia's population - but now the two main ethnic Albanian parties are bitter rivals.
"In most parts the vote was fair and democratic, but sadly in one part there were irregularities," Prime Minister Gruevski said.
"I will do everything in my power to have a re-run there so each and every MP is elected fairly," he added.
New polls were expected to take place within weeks.
Mr Gruevski aims to make Macedonia, a former part of Yugoslavia, a member of the European Union and of Nato. He called the election two years early, hoping to strengthen his hand and introduce reforms towards this end.
However, the EU said it was worried by the conduct of the poll.
EU Enlargement Commissioner Olli Rehn "is very concerned about the violence that occurred during the elections", his spokeswoman said.
She said the re-runs would be watched closely and the EU hoped to see "peaceful and orderly conduct of voting".