UNITA won 26.6 per cent of the vote and 51 parliamentary seats, while Casa-CE managed 9.5 per cent with 16 seats. The remaining three seats were shared by the FNLA and PNS.
The victory will allow outgoing 75-year-old President Jose Eduardo dos Santos to install a party loyalist, former defence minister Joao Lourenco, in his place after 38 years in power.
The MPLA has governed Angola since the country gained independence from Portugal in 1975.
The court must respond to the lawsuits within three days. If the outcome is unchanged, the inauguration ceremony will take place on September 25.
Claims of voting violations have been dismissed by Lourenco, who has accused the opposition of "spoiling the people's party".
"These political groups, by protesting in their sole interests against these so-called procedural irregularities, have violated electoral laws," he said late Wednesday.
The MPLA had predicted it would win easily, but the result showed a decline in support from the 2012 election.
The country of 28.8 million is battling high poverty levels and has suffered from a slump in crude prices in recent years.