Hundreds of thousands of angry protesters blocked the main road in Puerto Rico's capital on Monday in the largest demonstration yet seeking the resignation of the US territory's embattled governor.

Puerto Ricans are up in arms over alleged corruption involving money meant for victims of Hurricane Maria in 2017, which left nearly 3 000 dead.

They are also upset about the recent release of text chats in which Governor Ricardo Rossello and other officials make fun of journalists, gay people, women and hurricane victims, among others.

The demonstrators in San Juan were joined by some of the island's most famous singers, including Ricky Martin. The huge crowds sang, chanted, and danced in the streets during the mainly peaceful protest while carrying Puerto Rican flags.

Under mounting pressure, Rossello said on Sunday he will not seek reelection next year and will step down as leader of his party. But he refused to resign.

"I have listened, and I am listening to you today," Rossello said in a video posted on Facebook. "I have made mistakes and I have apologised."

That confession failed to appease demonstrators who have been taking to the streets for more 10 days demanding he step down.

"It is not enough. He should surrender power to new leaders," Isham Rodriguez, 36, said as he banged pots together while walking in Monday's march.

The crowd chanted slogans aimed at the governor, including "Ricky isn't here, Ricky is selling off what's left of the country".

US President Donald Trump also weighed in, calling Rossello "a terrible governor" and saying that hurricane relief funds were "in the hands of incompetent people and very corrupt people".

With protests showing no sign of abating, Rossello appeared on Fox News to try to defend his record.

"I used words that I've apologised for. I have also taken significant actions in the direction of helping vulnerable sectors in our population," he said.

Days earlier, prosecutors had ordered the arrest of six government officials accused of embezzling $15m in hurricane reconstruction money.

Calls for impeachment

Pop star Martin, who is gay, Puerto Rican and one of those ridiculed in the hundreds of pages of leaked Rossello chats, rejected the governor's gesture and joined the protest, carrying a gay pride flag.

"Ricardo Rossello, you are not only cynical, you are Machiavellian," Martin wrote on social media, as a slew of Puerto Rican artists, including Bad Bunny, Residente, Olga Tanon and others joined the demonstrations.

Martin urged lawmakers to begin impeachment proceedings against the governor.

"Corruption, it's insane. We are tired, we can't take it anymore," he said in a short clip posted from the protest to his 12.3 million Instagram followers.

"I do live in America but I had to come to Puerto Rico (to) let the world know that we will make a change. It's pretty much barbaric what he's doing, we're tired and we're angry."

Puerto Rican stars elsewhere voiced their support, including composer Lin Manuel Miranda, actor Benicio del Toro and "Despacito" singer Luis Fonsi.

San Juan mayor Carmen Yulin Cruz, who was also maligned in the text chats, also called for Rossello's impeachment.

"It is impeachment time. He's obstinate. His mental health isn't there. He doesn't want to resign," she told CNN.

Rossello said on Sunday he would face any proceedings "in a responsible manner".

Tear gas

Hundreds of people gathered in front of the governor's residence, chanting slogans such as "They will not stop us" and holding signs that said "Ricky resign".

Late on Monday evening, police dressed in riot uniforms fired tear gas to clear the area after protesters on the other side of a barricade lobbed objects at officers.

Puerto Rico was in dire straits even before Hurricane Maria, which laid bare the disastrous state of its electrical grid.

An economic crisis prompted the territory to seek protection from creditors under US bankruptcy law.

Budget cuts - which, among other actions, forced the closure of schools - prompted many Puerto Ricans to flee.

Combined with the post-hurricane exodus, Puerto Rico lost 4% of its population.

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