Caracas, Venezuela (CNN) -- President Hugo Chavez's ruling United Socialist Party of Venezuela won the most seats in Sunday's parliamentary elections but lost the supermajority that has allowed for quick passage of many of Chavez's programs and controversial measures.

The ruling party won 98 seats in the National Assembly, while an opposition coalition won 65, Chavez said Monday night. A leftist party not aligned with the government or the opposition picked up two seats.

Chavez needed 110 seats to keep the two-thirds supermajority his party has held in the assembly. Before the election, he held 137 seats.

Chavez called the election a victory for the governing party and played down the gains made by the opposition. He accused the opposition of exaggerating the impact of the seats they picked up. If they think they have a majority, they should call for a presidential recall referendum, Chavez said.

This marks the first time in five years that opposition parties will have a larger say in the nation's politics.

The opposition boycotted the last parliamentary elections in 2005 in protest against Chavez. As a result, though, that left Chavez's opponents without a strong voting bloc in the national assembly. It also gave Chavez's party the supermajority.

Critics say Chavez used that power in the National Assembly to transform the judiciary, the National Electoral Council and the military to serve his political purposes.

Nearly all of the assembly's seats were at stake Sunday. Some races were still too close to call when the first round of results were announced early Monday, said Tibisay Lucena, president of Venezuela's National Electoral Council.

Opposition leader Ramon Guillermo Aveledo said after the results were announced that officials had not mentioned a crucial figure. In the popular vote, he said, the opposition coalition won a 52 percent majority.

As he spoke, the crowd chanted, "Victory, victory, popular victory!"

While he criticized Venezuela's "perversion of an electoral system" that allowed a party to win the popular vote but have fewer seats in parliament, Aveledo said the elections were worthwhile.

"Even when we are competing at a disadvantage, even when the government ...has more resources. We think that, nonetheless, voting is always worth it," he said.

Even though Chavez was not on the ballot, the elections were widely seen as a referendum on his presidency, and he took an active role in this year's campaign.

Chavez hailed the results Monday, saying on his on-line Twitter account, "We have won a solid victory" and "We must continue strengthening the Revolution!"

The government-run Agencia Venezolana de Noticias also lauded the results, posting a story Monday morning that said "the Venezuelan public achieved a great victory."

Lucena announced the first round of results about eight hours after the official closing time for polls in the country's parliamentary elections. She said the delay in announcing the results was due to the closeness of the vote.

But opposition leader Aveledo said the delay was "unacceptable," given the technology available for tallying results.

Voters in Venezuela went to the polls Sunday to decide 165 of the 167 seats in the National Assembly.

In Venezuela, the electoral system is set up in a way that favors the majority party as well as rural votes more than urban votes. Chavez counts on support from the over-represented rural areas.

The system means that even if the opposition won at least half of the votes, it would actually seat considerably fewer than half of the parliament.

Although Venezuela has one of the highest murder rates in Latin America and an economy that is just beginning to recover from a recession, Chavez maintains support among many of Venezuela's poor.

But that support isn't as strong as before, as Venezuela faces electricity shortages and other infrastructure problems.

The Venezuelan embassy said more than 66 percent of the nation's 17.7 million registered voters participated in Sunday's elections.

"Sunday's election was the fifteenth time since 1998 that the Venezuelan people have gone to the polls to cast their ballots," the embassy said in Monday's release. "Over 6,400 candidates engaged in vibrant debate for the 165 available seats, and thousands of national and international observers were on hand to witness the electoral process."

CNN's Carlos Montero, Mariano Castillo and Catherine E. Shoichet contributed to this report.