JAKARTA — Indonesian police have named a fourth senior officer as a suspect in the alleged wiretapping of President Prabowo Subianto, deepening a scandal that has laid bare a widening rift between the president and his predecessor, Joko Widodo.

The development adds to mounting pressure on Mr. Prabowo, who faces growing public discontent over his costly populist policies and weakening investor confidence in Indonesia's $1.5 trillion economy — the largest in Southeast Asia and home to the world's fourth-largest population.

At a press conference late on Thursday, police identified the new suspect only by the initials SU, a senior law enforcement official who served as monitoring chief at Indonesia's Criminal Investigation Agency, the national police force's main investigative arm, between 2010 and 2019. Local media later identified him as Slamet Uliandi.

Cyber crime unit director Suhermanto said investigators allege that SU, who headed the agency's information and technology unit from 2021 to 2026, gave the go-ahead for the wiretapping. "When the other two suspects were about to wiretap, they got approval from SU. They also asked his approval before deleting interception records," Suhermanto told reporters, adding that SU had not yet been detained due to a health condition.

Three senior police officers had already been arrested on Tuesday, including former national police chief Listyo Sigit Prabowo, who serves as Mr. Prabowo's chief of staff and is widely known as a loyalist of Mr. Widodo. The arrest of the force's former top officer — head of the institution responsible for the country's law enforcement and internal security — underscored the seniority of those implicated in the case.

Investigators have yet to establish the motives behind the attempt to intercept the president's communications. They have so far questioned 13 police officers and five criminal and IT experts, and the national police chief has formed a special team to investigate the case, spokesperson Trunoyudo Wisnu Andiko said. That unanswered question of motive, along with whether SU is eventually taken into custody, now sits at the center of the special team's work.

Jakarta remained calm on Thursday and Friday despite the deployment of thousands of troops in the wake of the wiretapping revelations. Military tents and buses were seen in the capital, along with a small number of soldiers.

Separately, lawmakers are considering a probe into the eligibility of Vice President Gibran Rakabuming Raka, Mr. Widodo's son, who was Mr. Prabowo's running mate in the 2024 presidential election — a ticket that once linked the two families now at the center of the rift.

— Reuters