Guyanese President Irfaan Ali has claimed a second five-year term in office, even as official final results from Monday's general election are yet to be published.

Ali's People's Progressive Party (PPP) secured at least 242,000 votes in the poll, claiming majorities in eight of the 10 districts in the South American country, according to Reuters news agency.

We Invest in Nationhood (WIN), a new political party founded just three months ago, came in second with around 109,000 votes.

Ali, 45, campaigned on a pledge to use the country's vast oil reserves, discovered in 2019, to improve infrastructure and reduce poverty, while navigating territorial tensions with neighbour Venezuela.

It is not yet clear how many seats each party will have in the 65-member parliament, but the current vice-president, Bharrat Jagdeo, told local media that the PPP would have a "bigger majority" than at the last election in 2020.

Despite a lower turnout than at the last election, the PPP appeared to have increased its vote share - while the long-term opposition A Partnership for National Unity trailed in third.

Much of this election centred on how parties would manage revenues from massive oil reserves discovered by the oil giant ExxonMobil in 2019.

Since 2019, the company says it has found billions of barrels' worth of oil in Guyanese waters and territory - causing the state budget to quadruple.

With a population of around 800,000, Guyana now has one of the highest levels of proven crude oil reserves per capita in the world - and is one of the region's fastest-growing economies.

But opposition parties say there is unfair distribution of oil earnings to groups connected to the PPP, accusations the ruling party denies.

Businessman Azruddin Mohamed, leader of the WIN party, alleged voting irregularities in Monday's election, even as he celebrated the party having "shaken the pillars of Guyana's political establishment".

Observers from the Organization of American States were deployed to Guyana for the election and have not yet reported any instances of electoral fraud.

The election came the day after Guyanese police said that a boat carrying election officials and ballot boxes was "shot at from the Venezuelan shore" - in the contested Essequibo region.

Venezuela denied being behind the incident - which came as the two countries are locked in a dispute over competing claims to the oil-rich region.