The leader of the reformist Goran (Change) list, Nusherwan Mustafa, made the charge against Barzani's Kurdistan Democratic Party (KDP) shortly after the Kurdish prime minister condemned post-election violence that left one person dead and 12 wounded.

"There was lots of forgery in Arbil and Dohuk (provinces) to change the result and to go against the will of the people," Mustafa said in a statement addressed to, among others, UN Secretary General Ban Ki-moon and the British, French and US ambassadors to Iraq.

He called for pressure to be put on Barzani and the Iraqi electoral commission to "stop the forged results".

Goran claims to have won the most votes in Sulaimaniyah province and to have taken 28 seats in the 111-seat regional parliament overall.

But presidential cabinet chief Fuad Hussein said the recently formed party did not win in the region's other two provinces, Dohuk and Arbil.

Earlier, regional prime minister Nechirvan Barzani, the president's nephew and a KDP member, vowed to "take necessary measures" against party supporters who allegedly fired guns and shouted slogans outside the headquarters of the Islamic Kurdish Union in the regional capital Arbil.

He added that the gunfire had killed one person and wounded a dozen.

Police cordoned off the area surrounding the offices on Monday.

The Islamic Kurdish Union is a member of the leftist-Islamist Services and Reform list, which is expected to win as many as 17 seats in the regional assembly, according to unofficial projections.

Services and Reform has also complained of "fraud" and accused the region's two main parties of bussing unregistered voters to polling stations, claims that have been dismissed by Iraq's electoral commission.

The regional premier made no mention, however, of vandalism of Goran offices.

Goran offices in Arbil were ransacked on Sunday by suspected KDP supporters as unofficial results started to filter out.

"They entered three of our offices, broke everything and plastered the walls with photos of (Massud) Barzani," said Goran official Othman Dachki, adding that assailants had also tried but failed to attack the Goran television station, Kurdistan News Network.

"We hold the (Kurdish) authorities responsible because they cannot guarantee competition between parties in a spirit of fair play," he said, adding there were no casualties.

Several Goran members are defectors from Iraqi President Jalal Talabani's Patriotic Union of Kurdistan (PUK) -- Mustafa himself is a former PUK deputy leader -- who quit the party just months before the elections to protest at what they claim is the PUK's unwillingness to reform and fight corruption.

The long dominant KDP and PUK -- both former rebel factions that fought successive regimes in Baghdad -- campaigned for Saturday's election on a joint list and had been firm favourites to emerge victorious.

Electoral commission official Hamdia al-Husseini said that full preliminary results would not now be released before Monday because of delays in the count in Sulaimaniyah and Dohuk provinces.

Final results are not expected for several days afterwards as ballots must first be transferred to Baghdad for an offical tally.

Nearly 80 percent of the region's 2.5 million voters took part in what poll officials trumpeted as a transparent election.

The vote was held at a key time in Iraq's transition as regional leaders are locked in a bitter dispute with Baghdad over land and oil, while local voters also voiced increasing concern over corruption.