MAPUTO — Mozambique's President Filipe Nyusi was on Tuesday forecast to be heading for a landslide victory in an election the opposition says has been tarnished by fraud while observers reported numerous irregularities.

Some polling stations recorded many more votes than registered voters in last week's ballot, the Electoral Institute for Sustainable Democracy in Africa (EISA) said, reporting that some its observers have been obstructed.

EISA said it detected the irregularity while calculating its own estimation of the outcome, which suggests Nyusi will win more than 70 percent of the vote.

Though official results have yet to be announced and the count is continuing, former guerrilla movement turned main opposition party Renamo has already rejected the outcome, decrying problems in the process from voter registration through to counting.

That threatens a fragile peace accord signed just months ago between its presidential candidate, Ossufo Momade, and Nyusi, and in turn the stability of nation on the verge of becoming a global gas exporter.

EISA programme officer Domingos Rosario told a news conference that at many polling stations in seven provinces, the number of votes greatly exceeded the number of voters.

He said some observers had been prevented form carrying out their work.

A spokesman for the Electoral Administration Technical Secretariat did not respond to multiple requests for comment on fraud accusations nor the pace of the official count.

Two-thirds of polling stations have been processed, representing just over 36 percent of the more than 13 million potential ballots from registered voters, according to data on the electoral commission's website.

So far, Nyusi has taken 74.6 percent of the presidential vote versus 20.2 percent for Momade.

EISA estimates Momade will end up with around 21.4 percent of the vote while Daviz Simango, of smaller rival the Mozambique Democratic Movement, will secure 6.9 percent. It based its estimations on data from just under 2,500 polling stations.

Renamo and Nyusi's party, the ruling Frelimo, fought on opposite sides of a 16-year civil war that ended in a truce in 1992, but the former foes have clashed sporadically since.

The pact was meant to bring a definitive end to four decades of violence between the two, shoring up Mozambique's stability just before blockbuster gas projects in the gas-rich north led by the likes of Exxon Mobil Corp and Total take off.

Instead, it is at risk of collapse as tensions rise. That would draw focus and resources away from the government's battle against an Islamist insurgency on the projects' doorstep.

Renamo's performance in provincial elections in a handful of central and northern provinces — its traditional heartlands — is seen as central to the deal's survival.

For the first time, provincial governors will be appointed by the majority party in each province rather than the government in Maputo - a key opportunity for Renamo to satisfy a long-thwarted desire for representation.

However the party has already lost a number of them to Frelimo, according to the state news agency, including Nampula, Sofala and Zambezia — among those where EISA detected mismatches.

Overall, with 48.73 percent of polling stations processed, Frelimo has taken 74.3 percent of the provincial vote while Renamo drifts behind on 20.3 percent, according electoral commission data.

At a parliamentary level, where 52 percent of polling stations have been processed, Frelimo leads with 76.25 percent of the vote compared to just shy of 17 percent for Renamo.

Frelimo spokesman Caifadine Manasse said Renamo regularly complains about elections, despite being part of all the electoral bodies and having delegates at voting stations.

"Renamo is not serious about democracy," he said. — Reuters