MANILA, Philippines - A senator from the Philippines was detained on Monday and indicted under national anti-corruption laws, marking the most recent case of an upper house member taken into custody within the past month on suspicions of widespread graft.

Sen. Rodante Marcoleta, who rejects all allegations of misconduct, was placed under police custody at the Sandiganbayan special anti-graft court in suburban Quezon City after arriving with legal counsel to challenge the accusations and request postponement of detention.

He faces a plunder charge, which Philippine statutes define as the illegal accumulation of substantial wealth via repeated criminal acts, and such charges preclude any possibility of bail.

"Let's respect that," Marcoleta, a 72-year-old attorney, stated outside the courtroom in reference to the judicial order for his arrest following an initial review of evidence. Authorities then escorted him away.

Marcoleta is affiliated with Iglesia ni Cristo, or Church of Christ, whose members organized a three-day demonstration involving over 15,000 participants at a key democracy site along Manila's primary thoroughfare to oppose the charges and upcoming detention, resulting in significant traffic disruptions.

President Ferdinand Marcos Jr. postponed two scheduled official events outside his office on Tuesday amid concerns regarding the demonstration by the influential religious organization known for mobilizing large-scale gatherings.

The Office of the Ombudsman, serving as the primary anti-graft authority, reported filing the plunder charge against Marcoleta the previous week for allegedly accepting 75 million pesos ($1.2 million) in purported campaign donations from three backers that went undeclared in required asset filings.

Two of those donors, among them former House member Mike Defensor, were also detained on Monday, according to Interior Secretary Jonvic Remulla.

Early last month, Sen. Jinggoy Estrada, a political associate of Marcoleta, was similarly arrested and held without bail on plunder charges tied to alleged kickbacks from a flood-control initiative.

Estrada, 63, has firmly rejected claims primarily from a former public works engineer that he accepted over 570 million pesos ($9.3 million) in project-related kickbacks.

Marcoleta and Estrada both backed former President Rodrigo Duterte and his daughter, Vice President Sara Duterte. The 24-member Senate, functioning as an impeachment body, was set to begin proceedings later Monday against Sara Duterte following her impeachment by a strong House majority in May.

She has rejected the accusations of serious offenses, such as accumulating undeclared assets and issuing public threats against the president.

A third senator aligned with the Dutertes, Ronald dela Rosa, has gone into hiding following an International Criminal Court arrest warrant naming him as a co-perpetrator with the former president in the deaths of mostly impoverished suspects during a violent anti-drug operation led by Duterte.

Dela Rosa served as Duterte's national police chief and initially implemented the crackdowns. The former president was detained last year under ICC directives and transported to the Netherlands for a trial scheduled to begin Nov. 30 on alleged crimes against humanity.