Hundreds of thousands of people on Sunday gathered in Manila for a three-day rally to demand accountability for a flood-control corruption scandal involving top government officials and lawmakers.

"We come together not to meddle in politics, but to stand with our fellow Filipinos who are calling for truth after more than 100 days of unanswered wrongdoings," organizers said in a Facebook post.

"This peaceful movement demands a thorough, fair, and constitutional investigation because corruption has harmed every Filipino, yet no one has been held accountable," it added.

Outrage has been growing in the Philippines since President Ferdinand Marcos Jr. revealed the scandal in his annual state of the nation address in July, which followed weeks of deadly flooding.

What's the Philippines' flood-control corruption scandal about?

The corruption scandal centers on government-funded flood-control projects, which were revealed to be substandard or even nonexistent.

Private contractors are accused of pocketing funds through ghost projects or delivering subpar infrastructure in areas that are now severely affected by flooding.

Whistleblowers have named some legislators, alleging they received kickbacks from construction companies.

Flood control is a sensitive issue in the Philippines, one of the most vulnerable countries to the climate crisis.

What's being done about the Philippines' graft scandal?

Organized by an independent Christian church (INC) in the Philippines, Sunday's rally was so far the largest mass protest against the corruption scandal.

It comes on the heels of two typhoons that left more than 250 people dead, many due to flash floods and landslides.

In an attempt to quell public outrage and street protests, Marcos said Thursday that many senators, members of Congress and businesspeople implicated in the case would be in jail by Christmas.

He said an independent fact-finding commission he created earlier this year to investigate the alleged corruption has already filed criminal complaints against 37 suspects.

Marcos is aware of the power of public anger. His late father, Ferdinand Marcos Sr., was ousted by the People Power Revolution, which was sparked by widespread anti-corruption sentiment, in 1986.

Edited by: Kieran Burke