LUANDA (Reuters) - The leader of Angola s main opposition party called on the country s electoral commission on Saturday to explain how it compiled provisional election results giving the ruling MPLA party a landslide victory. Isaias Samakuva said his UNITA party, which has rejected the published results of Wednesday s national ballot, was conducting a parallel count using polling station records and computer software that did not tally with the commission s figures.  Where did those results come from?  Samakuva asked supporters at the party s campaign headquarters in Luanda.  The CNE (commission) must explain to Angolans what it did wrong and why it did it.  Based on nearly 98 percent of the vote counted, CNE figures announced on Friday put the People s Movement for the Liberation of Angola (MPLA) on 61.1 percent and the National Union for the Total Independence of Angola (UNITA) on 26.7 percent. Definitive results may not be announced until Sept. 6. International observers described the election as reasonably free and fair and the mood in Luanda has remained calm. UNITA said the results released so far were not legally binding and it would release its national tally early next week.  The country still doesn t have a President-elect,  Samakuva said. President-in-waiting Joao Lourenco, a former defense minister, is set to become the country s first new leader for 38 years, replacing Jose Eduardo dos Santos, who will continue as head of the MPLA. UNITA and smaller opposition party CASA-CE say the provisional results were processed without input from provincial counting centers or certain representatives on the electoral commission, going against Angolan law. The commission has said the process of vote-counting was  going well  but has not extensively explained how provisional numbers were tallied.  Even if the parties have summary records of the polling stations and minutes of electoral operations, it is necessary to realize there is another set of elements and documents that will contribute to the provincial and national tally and this information is not available to the parties,  commission spokeswoman Julia Ferreira said on Friday, without elaborating. UNITA published on Friday its parallel count for four provinces   Huambo, Bie, Cabinda and Luanda   which in all cases showed the party doing better than the commission results indicated. The MPLA, which emerged victorious over UNITA after 27 years of civil war in 2002, has dismissed the complaints, saying its old foe always take issue with election results.  