Xalapa (Mexico) (AFP) - Mexico's ruling PRI party was trailing early Monday in key races for governor in elections considered as a test for its hopes of retaining the presidency in 2018.
Results trickled in slowly late into the night in 12 states, out of 32, that voted Sunday for new governors following an election day marked by incidents of violence.
President Enrique Pena Nieto's Institutional Revolutionary Party (PRI) holds the governorship in nine of the states up for grabs.
But early official results showed the PRI leading in just five states while losing its grip on two key states, Tamaulipas and Veracruz, which it has controled for more than 80 years.
The conservative National Action Party (PAN) was leading in six states, including two where it partnered with the left-wing Democratic Revolution Party (PRD). The leftist Morena party was ahead in Veracruz.
PRI leader Manlio Fabio Beltrones had voiced confidence of victory in nine states, declaring "today we can say that Mexico chose PRI."
PAN chief Ricardo Anaya had claimed wins in three states, the most his party had won in a single election.
"We have broken the authoritarian monopoly the PRI has had for 86 years," Anaya said.
All three candidates in the oil-rich eastern state of Veracruz declared victory, even though final results were not due for hours.
"We didn't just defeat a political party. We defeated a corrupt system," said Miguel Angel Yunes, candidate of a coalition of the PAN and the leftist Democratic Revolution Party (PRD).
But with 24 percent of the votes counted, Cuitlahuac Garcia Jimenez of the left-wing Morena party held a slight lead, with 32.2 percent. Yunes had 31.5 percent while his cousin, the PRI's Hector Yunes Landa, had 26.8 percent.
Veracruz has been run since 2010 by the unpopular Governor Javier Duarte, whose administration has been marred by drug violence and the killings of 18 journalists.
Victory for Morena would boost two-time failed presidential candidate Andres Manuel Lopez Obrador, who founded the movement after leaving the PRD in 2012.
Veracruz remained a PRI stronghold even after the party lost its 71-year grip on the presidency in 2000. Pena Nieto returned the PRI to power in 2012.
- A human head -
The opposition reported several incidents in Veracruz, including people receiving anonymous text messages warning them not to vote.
A human head was found Saturday in a park near a school serving as a polling place in the town of Emiliano Zapata, with a threatening note against a PAN-PRD candidate for the state legislature.
Before dawn on Sunday, unknown assailants set fire to the house of a PAN mayor in Acajete, the party said.
In another incident, the PAN said armed assailants stole computers from a candidate's headquarters.
Election officials said several people wielding baseball bats struck voters and tried to break ballot boxes in one town.
- Footballer's kidnapping -
In Tamaulipas, the PRI and PAN exchange accusations of bowing to pressures from drug cartels.
With 37 percent of the votes counted, PAN candidate Francisco Garcia Cabeza de Vaca led with 49.8 percent compared to 35.6 percent for the PRI's Baltazar Hinojosa.
In 2010, PRI gubernatorial candidate Rodolfo Torre Cantu was assassinated. His brother, Egidio, was elected.
The election was rocked by last week's kidnapping of football player Alan Pulido, a striker with Greek club Olympiakos who managed to fight off a kidnapper and call police just 24 hours after his abduction.