(Adds Gruevski comments)
By Kole Casule
SKOPJE, April 28 (Reuters) - Macedonia's conservative ruling party has secured a third term in office, winning both parliamentary and presidential elections on Sunday, based on preliminary results of the ballot that the opposition said it would not recognise.
With more than 63 percent of the votes counted, Prime Minister Nikola Gruevski's VMRO-DPMNE was leading with 43 percent, compared with 24 percent for the main opposition party, the centre-left SDSM, the state electoral commission said.
Incumbent President Gjorge Ivanov also was leading the SDSM-backed challenger in the presidential election, the commission said.
"This is a big, huge and strong victory. The people have clearly expressed their will," Gruevski, who has ruled the former Yugoslav republic since 2006 in coalition with the ethnic Albanian party DUI, told a cheering crowd at his party's headquarters in Skopje early on Monday.
The DUI had captured 14 percent, setting the coalition on course for a comfortable majority in the new parliament.
SDSM leader Zoran Zaev, however, accused Gruevski and his party of "abusing the entire state system", saying there were "threats and blackmails and massive buying of voters" in the elections.
"A few minutes after the polls closed, I'm here to say that SDSM and our opposition coalition will not recognise the election process, neither the presidential nor the parliamentary," Zaev told reporters in Skopje.
Gruevski, 43, and his party dismissed the opposition allegations as an attempt to manipulate public opinion.
"I'm sorry that besides our clear victory, the leader of the opposition for his personal interest has decided to ignore the will of the people. I hope he'll sleep on it and will decide to change the decision."
Monitors from the Organisation for Security and Cooperation in Europe will present their findings later on Monday, after the state electoral commission publishes the results.
Opposition parties have often accused Gruevski of creeping authoritarianism and corruption. Foreign diplomats in Skopje say there are concerns about media freedom and political pressure on journalists.
Gruevski has said any complaints of authoritarianism come from opposition parties that lack a concrete political programme to unseat him. He has dismissed as false the corruption charges and has threatened lawsuits against SDSM's Zaev.
It was not immediately clear what concrete steps the opposition would take once the results are officially confirmed. The SDSM said it was "keeping all options open and would decide in the next few days".
Macedonia, with a population of 2 million, remains one of Europe's poorest countries. Unemployment is above 28 percent, but Gruevski's government has achieved solid economic growth, low public debt and a rise in foreign investment, unlike most other Balkan countries.
Diplomats have also praised Gruevski for keeping in check tensions between Macedonia's Slav majority and its large ethnic Albanian minority, whose rebellion in 2001 to secure more political rights brought the country to the brink of civil war.
But during his eight years in office, Skopje's bid to join the European Union and NATO has been frozen because of a dispute with neighbouring EU member Greece over Macedonia's name, which Athens wants changed because it is also the name of a northern Greek province.
Macedonia became a formal candidate for EU membership in 2005 but has made no progress since, as Greece has continued to block it. Years of U.N.-mediated talks have yielded no results.
The parliamentary election was called a year ahead of schedule, after the coalition partners failed to agree on a joint candidate for president. (Writing by Zoran Radosavljevic; Editing by Mohammad Zargham and Paul Simao)