According to an estimate from the National Electoral Institute (INE), President Enrique Pena Nieto's (photo) Institutional Revolutionary Party (PRI) and its allies the Green Party and the smaller New Alliance Party (PANAL) have increased their majority to 260 seats in the 500-member lower house.

Nevertheless, the PRI and its allies saw their overall share of the vote fall two percentage points from the last elections in 2012. They captured almost 40 percent of the ballots.

The PRI's closest rival, the National Action Party (PAN), saw its share of the vote decline five points to 21 percent.

The main leftist opposition group, the Party of the Democratic Revolution (PRD) only won 56 seats, about half the number it had going in to the election.

A larger number of independent candidates and smaller parties split the vote. A new leftist party, Morena, formed by two-time presidential runner-up Andres Manuel Lopez Obrador, was projected to win 35 seats.

The PRI, Green Party and PANAL did well in the election for the 300 seats awarded by relative majority, according to the INE estimate. This is where the party with most votes in a constituency wins.

The remaining 200 lower house seats are divided between the parties by proportional representation of the overall voting.

The small, left-leaning Labor Party (PT) was not expected to clear the three percent vote hurdle needed to enter Congress. Any seats it would have won through proportional representation would be redistributed among the other parties.

Confirmed results

The INE estimate is expected to be confirmed on Sunday.

The result could be affected by recounts or appeals to the electoral tribunal. The final, confirmed results are due before July 23.

The run-up to the poll was marked by violence with drug cartels blamed for the deaths of several candidates. Teachers' unions also called a boycott to protest the privatization of education.

Elections for the Senate, the 128-seat upper house, are not due until 2018.

jm/bk (Reuters, dpa)