With 75 per cent of votes counted by midday on Wednesday, the election commission said Jagdeo's People's Progressive Party/Civic (PPP/C) had more than 150,000 votes to 93,000 for the main opposition party, the People's National Congress Reform (PNCR), headed by lawyer Robert Corbin.
Jagdeo, a Moscow-trained economist who has promised better government services and crime-fighting in the impoverished former British colony, looks likely to keep a majority in the 65-member parliament.
Jagdeo won support by building schools, water pipelines and roadways and by reducing the country's debt. But Guyana, which is about the size of Britain with a population of just 750,000, still struggles with high crime rates, growing drug trafficking and a lack of investment despite rich timber and bauxite reserves.
Gocool Boodoo, Guyana's chief elections officer, said: "We are working towards official final results by 8pm or, if not, very early in the morning."
The Guyana election commission said that some 75 per cent of the 492,000 eligible to vote did so.
Crime as poll issue
Results released by the election commission on Wednesday showed that newcomers Alliance for Change (AFC) had about 23,000 of the votes counted so far.
Crime rates became the focus of electoral campaigning after several high-profile killings shocked the country. Earlier this year a minister was gunned down in his home and five newspaper workers were slain.
"We are working toward official final results by 8 p.m. or, if not, very early in the morning,"
Guyana's chief elections officer
Jagdeo, who worked his way up the party ranks after entering politics as a teenager, was favoured to win the election in the small South American nation, where tensions between the ethnic Indian majority and Afro-Guyanese have marred three previous votes.
Monday's poll went ahead without any violence but Georgetown remained edgy as residents waited for possible reactions from Jagdeo's foes. Soldiers were dispatched to the streets during and after the vote.
Elections in 1992, 1997 and 2001 ended in rioting and several deaths when tensions between the two main parties exploded into violence and looting.
South America's only English-speaking country, Guyana gained its independence from Britain in 1966.
Most residents are either descendents of African slaves or of indentured workers brought from India and China to work on sugar cane plantations.
Most Guyanese are children of
African slaves or Indian workers
The ethnic Indian majority mostly backs Jagdeo's ruling PPP/C. Corbin and the PNCR claim support primarily from Guyanese who trace their roots back to Africa.
Jagdeo said on Tuesday that he was confident of victory, but Corbin denounced irregularities and accused the ruling party of fraud at one polling station.
Observers, including teams from Commonwealth nations and the Organisation of American States, noted some difficulties in the ballot but said they would not affect the outcome.
Corbin said his party had discovered collusion at some polling stations between election officials and poll workers from the ruling party, which had allowed unregistered voters to cast ballots. He said he would challenge those results.