San Juan, Puerto Rico -- Puerto Rico braced early Monday for what many people expected to be one of the biggest protests ever seen in the U.S. territory as irate islanders pledged to drive Gov. Ricardo Rosselló from office.

Hundreds of thousands of people were expected to take over one of the island's busiest highways Monday morning to press demands for the resignation of Rosselló over an obscenity-laced leaked online chat the governor had with allies as well as federal corruption charges leveled against his administration.

Activists believe it will become a key moment in the political turmoil that has beset Puerto Rico for more than a week.

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Anger erupted Sunday night in the city of Guaynabo where demonstrators had trapped a group of legislators inside a community center where earlier there was a meeting with Gov. Rosselló. The governor managed to leave with his bodyguards before the other legislators became trapped, reports CBS News' David Begnaud.

The anticipated march in the capital, San Juan, would come a day after the 40-year-old Rosselló announced he wouldn't quit, but sought to calm unrest by promising not to seek reelection or continue as head of his pro-statehood political party. That only further angered his critics, who have mounted street demonstrations for more than a week.

"The people are not going to go away," said Johanna Soto, of the northeastern city of Carolina. "That's what he's hoping for, but we outnumber him."

Former New York City Council Speaker Melissa Mark-Viverito, one of the most prominent Puerto Rican politicians in the mainland and a target of sexist comments in the leaked chat Rosselló was part of, said the governor's move is not enough. She faulted Rosselló — who called her a "whore" in the leaked messages — for failing to fully address the public's many grievances in his statement on Sunday.

"People don't want to hear that. There's a clear sign that people will not accept anything other than his resignation," Mark-Viverito told CBS News. "And the fact that he refuses to do that is irresponsible. It's anti-Democratic and it's just fueling the tensions."

People watch a television broadcast of Puerto Rico's governor Ricardo Rossello's speech, at a bar in San Juan on July 21, 2019 GABRIELLA N. BAEZ / REUTERS

"The only choice he has is to resign," she added. "That is what the call of the people is about."

Organizers labeled the planned road shutdown "660,510 + 1," which represents the number of people who voted for Rosselló plus one more to reject his argument that he is not resigning since he was chosen by the people.

Monday would be the 10th consecutive day of protests, and more were being called for later in the week. The island's largest mall, Plaza de las Américas, closed ahead of the protest as did dozens of other businesses.

In a video posted Sunday night on Facebook, Rosselló said he welcomed people's freedom to express themselves. He also said he was looking forward to defending himself against the process of impeachment, whose initial stages are being explored by Puerto Rico's legislature.

"I hear you," he said the brief video. "I have made mistakes and I have apologized."

The 889 pages of chat on the encrypted app Telegram between the governor and 11 close allies and members of his administration, all men, showed the governor and his advisers insulting women and mocking constituents, including the victims of Hurricane Maria.

Hours after Rosselló spoke Sunday, another top government official submitted his resignation. "Unfortunately the events in recent weeks, including the attitudes reflected in the comments of officials and advisers of the current administration, do not match my values and principles," wrote Gerardo Portela, principal investment officer, president of Puerto Rico's Economic Development Bank and executive director of the Housing Finance Authority.

Since the chat leaked July 13, hundreds of thousands of Puerto Ricans have marched to Rosselló's official residence in the largest protest movement on the island since Puerto Ricans successfully demonstrated to bring an end to U.S. Navy military training on the island of Vieques more than 15 years ago.

Demonstrators march against Puerto Rico Gov. Ricardo Rosello in San Juan on July 17, 2019 Dennis M. Rivera Pichardo / AP

Ramphis Castro of Guayama arrived in San Juan late Sunday after more than an hour-long drive to prepare for Monday's march. He said he was incensed after Rosselló's announcement Sunday.

"When is he going to say that he's resigning," Castro exclaimed. "This makes people even more angry."

The upheaval comes as the U.S. territory is struggling to recover from Hurricane Maria and trying to restructure part of $70 billion in debt amid a 13-year recession in this territory of more than 3 million American citizens who do not have full representation in Congress or a vote for president.

Normally, a governor who resigns would be replaced by Puerto Rico's secretary of state, but Luis Rivera Marín quit that job amid the uproar over the chat, so the next in line would be the justice secretary, Wanda Vázquez.

Pressure on Rosselló to step down has intensified as the chorus calling for his resignation grew to include Puerto Rico music superstars Ricky Martin, Bad Bunny and Residente and a string of U.S. politicians including Congress members from both parties, several Democratic presidential candidates and Puerto Rico's non-voting representative in Congress.

Rosselló was elected governor in November 2016 with nearly 50% of the vote, and he had already announced his intention to seek a second term. A graduate of MIT with a doctorate in genetics, he is the son of former Puerto Rico Gov. Pedro Rosselló, who flew to the island to marshal support after the chat was made public.

The governor belongs to the New Progressive Party, which seeks statehood for the island, and is also a Democrat. Most of his time has been spent seeking federal funds since Hurricane Maria devastated the island on Sept. 20, 2017, and battling austerity measures implemented by a federal control board that Congress set up to oversee the island government's finances.

The upheaval against Rosselló prompted at least four cruise ships to cancel visits to Puerto Rico, and many officials worry about the impact a resignation would have on the already fragile economy as the island rebuilds from Maria, a Category 4 storm that caused more than an estimated $100 billion in damage.

Another concern is the recent string of arrests involving federal corruption charges targeting Puerto Rico officials, among them two former agency heads, including former education secretary Julia Keleher.