Mexico's main leftist party holds a slight lead today in an election in the state of Chiapas to add to tension over a contested July 2nd presidential vote.
Juan Sabines of the left-wing Party of the Democratic Revolution (PRD) had 48.43 per cent of the vote with votes in from 93 per cent of polling stations in the largely Maya Indian state, a lead of just 0.29 percentage points over his main rival, according to electoral authorities.
A hefty 5 per cent of ballot box returns had irregularities, meaning the final result will likely be challenged. Chiapas has a long history of political violence and is home to Zapatista rebels who took up arms in 1994.
The PRD's presidential candidate, Andres Manuel Lopez Obrador, has claimed fraud after narrowly losing the July 2nd election, and there have been weeks of protests that have raised tension in the country and brought chaos to the centre of Mexico City.
A victory for his party in Chiapas would bolster Lopez Obrador's bid to build a national campaign to prevent his conservative rival, Felipe Calderon of the ruling National Action Party (PAN) from taking office.
Ecstatic supporters mobbed Mr Sabines and sang in celebration when he declared himself the winner of a divisive race on Sunday night.
But supporters of rival candidate Jose Antonio Aguilar Bodegas also claimed victory and held noisy celebrations in the state capital of Tuxtla Gutierrez.