SAN JUAN, PUERTO RICO -- Puerto Rico on Sunday was forced to partially suspend voting for primaries marred by a lack of ballots as officials called on the president of the U.S. territory's elections commission to resign.

The primaries for voting centres that had not received ballots by early afternoon are expected to be rescheduled, while voting would continue elsewhere, the commission said.

"I have never seen on American soil something like what has just been done here in Puerto Rico. It's an embarrassment to our government and our people," said Pedro Pierluisi, who is running against Gov. Wanda Vazquez, to become the nominee for the pro-statehood New Progressive Party.

Meanwhile, Vazquez called the situation "a disaster" and demanded the resignation of the president of the elections commission.

"They made the people of Puerto Rico, not the candidates, believe that they were prepared," she said. "Today the opposite was evident. They lied."

A federal control board that oversees Puerto Rico's finances issued a statement saying the "dysfunctional" voting process was unacceptable and blamed it on what it said was inefficiency by the elections commission.

The unprecedented situation comes amid a spike in COVID-19 cases in Puerto Rico, an island of 3.2 million people that has reported more than 12,800 probable cases, more than 8,500 confirmed cases and at least 274 deaths.

Gireliz Zambrana, a 31-year-old federal employee, worried about the number of people gathered at a voting centre in Rio Grande as they huddled together while waiting for it to open.

"They were trying to get away from the sun," he said, adding that he never got to cast his vote.

The president of the governor's party, Thomas Rivera Schatz, along with the president of the main opposition Popular Democratic Party, held a joint press conference and said they agreed the remaining primaries should be held on Aug. 16, a move that Vazquez said she supported. The two parties are both holding their primary elections with the winning nominees among six gubernatorial candidates in November's general election.

Other politicians argued that the entire primary be scrapped and held at another date.

An incredulous Schatz noted that there were still trucks with ballots inside parked at the commission's headquarters as they spoke there.

"The question is, why haven't they left?" he said.

A commission spokeswoman said officials were not immediately available for comment.

To further complicate things, Edgardo Roman, president of the Bar Association of Puerto Rico, told The Associated Press that it's unclear what alternatives are legally viable because the island's electoral law is not clear.

"It doesn't contemplate this scenario," he said.

Hundreds of frustrated voters who wore the required face masks and braved a spike in COVID-19 cases were turned away from centres across Puerto Rico as officials told them that no ballots were available.

The situation infuriated voters and politicians of all stripes as they blamed Puerto Rico's elections commission and demanded an explanation for ballots reaching only a handful of voting centres by the afternoon.

"This is indignant, abusive and an attempt against the democracy of our country," said Marcos Cruz, mayor of the northern town of Vega Baja that was still awaiting ballots.

Meanwhile, officials from the island's two main parties scrambled to find solutions as they urged voters to still show up at centres that remained open.

Yadira Pizarro, a 44-year-old teacher, ran out of patience at a shuttered voting centre in Carolina where she had waited more than four hours under a blistering sun.

"I cannot believe this. This is some serious negligence," she said.

One of the most closely watched races on Sunday is that of the pro-statehood Progressive New Party, which pits two candidates who served as replacement governors following last year's political turmoil. Vazquez faces Pierluisi, who represented Puerto Rico in Congress from 2009 to 2017.

Pierluisi briefly served as governor after Gov. Ricardo Rossello resigned in August 2019 following widespread street protests over a profanity-laced chat that was leaked and government corruption. But Puerto Rico's Supreme Court ruled that Vazquez, then the justice secretary, was constitutionally next in line because there was no secretary of state.

Meanwhile, the main opposition Popular Democratic Party, which supports Puerto Rico's current political status as a U.S. territory, is holding a primary for the first time in its 82-year history. Three people are vying to become governor -- San Juan Mayor Carmen Yulin Cruz, known for her public spats with U.S. President Donald Trump following the devastation of Hurricane Maria; Puerto Rico Sen. Eduardo Bhatia; and Carlos Delgado, mayor of the northwest coastal town of Isabela.