MEXICO CITY: Mexican President Enrique Pena Nieto’s slim working majority in the lower house of Congress hung in the balance on Monday after mid-term elections held amid widespread anger over corruption, gang violence and weak economic growth.

Mexicans cast votes on Sunday for the 500-strong lower house as well as nine state governorships and more than 1,000 state and municipal posts in what was seen as a referendum on Pena Nieto’s rule. The Senate was not up for renewal.

By early Monday morning, with nearly three-quarters of polling station returns, preliminary results showed that Pena Nieto’s Institutional Revolutionary Party (PRI), along with its allies, the Green Party and the smaller New Alliance Party, had won 38.94 percent of the vote.

The PRI and its coalition partners had a one-seat majority of 251 seats heading into the vote, having won around 42 percent of the vote in the 2012 election.

Early forecasts from Mexico’s electoral authority INE had shown the PRI and its partners winning between 246 and 263 of the 500 seats in the lower house.

The PAN had 20.76 percent of the vote, the preliminary results showed.

At least seven candidates and nine campaign officials were murdered in campaigning blighted by drug cartel intimidation and dissident teachers protesting against education reforms.