UN reports show that infant mortality in Equatorial Guinea is increasing, while education enrolment has dipped since oil was discovered in 1994.
Obiang said before the polls that he expected to at least match the 97 per cent of the vote he took in the last poll in 2002, which was widely criticised for fraud.
Sunday's vote was also widely criticised for irregularities, with claims that election observers were given scant access and that foreign media were barred from covering the election.
Pro-democracy groups complained about the lack of media time given to rivals.
"In recent weeks it [the government] has stifled and harassed the country's beleaguered political opposition ... [and] imposed serious constraints on international observers," New York-based Human Rights Watch (HRW) said in a statement.
Critics have accused Obiang, who has ruled Equatorial Guinea since 1979, of attacking and harassing opposition politicians, and having the election organised by his own ministers.
'Isolated and disappointed'
Western governments have also been accused of ignoring widespread rights abuses and repression, in favour of dealing with the West African nation which has large oil and gas reserves.
"We feel isolated and disappointed because we are doing what little we can while those who have interests in this country should be putting pressure on this regime," Wenceslao Mansogo Alo, a human rights representative of the main opposition Convergence for Social Democracy, said before the vote.
"Countries like the United States and the European Union have the power to intervene with this dictatorship."
Equatorial Guinea is the third largest producer of oil in sub-Saharan Africa, aiding the country's annual per capita income rise to $31,000, the highest in the region.
However, more than 60 per cent of its about 600,000 citizens still live on less than $1 per day.