Human rights groups are questioning the validity of Sunday's referendum in Equatorial Guinea, which officials say resulted in near unanimous support for proposed constitutional reforms.

New York-based Human Rights Watch and Equatorial Guinea's EQ Justice said Tuesday some polling places did not even have ballots available that would have registered a “no” vote.

Voters, observers, and opposition officials told the human rights groups they saw people encouraged to vote publicly as well as to cast ballots on behalf of absent relatives. They also saw military forces in and around some polling places. They said opposition members were threatened and two were detained.

Officials said preliminary results showed about 99 percent of votes in favor of the reforms, which include new presidential term limits and the creation of a vice presidency.

Critics say the new constitution will increase President Teodoro Obiang Nguema's authority and allow him to handpick his successor.

The opposition says Mr. Obiang would likely choose his son to fill the vice presidential slot.

Mr. Obiang's government says the reforms will provide better oversight of the executive branch, and improve both human rights and the judicial system.

The new constitution also removes an existing maximum age limit for the president, which would allow the 69-year-old Obiang to continue running for president after he turns 75.

Mr. Obiang has been in power since 1979. The anti-corruption group Transparency International ranks Equatorial Guinea among the world's 12 most corrupt countries.

The U.S. Department of Justice recently accused President Obiang's son of stealing, extorting, and embezzling more than $100 million and laundering most of the money in the United States.

Human Rights Watch says Teodoro Nguema Obiang Mangue is also under investigation for corruption and money laundering in France and Spain.