JAKARTA (Reuters) - Indonesia’s anti-graft agency on Tuesday condemned an acid attack on one of its top investigators handling a corruption investigation that has implicated dozens of politicians, and said it would not be deterred in its fight.

The speaker of Indonesia's parliament, Setya Novanto, waves before meeting with Indonesian President Joko Widodo at the Presidential Palace in Jakarta, Indonesia March 14, 2017 in this photo taken by Antara Foto. Antara Foto/Puspa Perwitasari via REUTERS

The corruption investigation, involving the suspected theft of $170 million from a budget to procure national electronic identity cards, is turning into one of the biggest cases the agency, known by its Indonesian initials KPK, has handled.

The KPK has banned the speaker of parliament, Setya Novanto, from overseas travel for six months in connection with the case, which has stirred sensational headlines in Southeast Asia’s biggest economy long burdened by endemic graft.

Early on Tuesday, an unidentified attacker threw acid at senior KPK investigator Novel Baswedan, police said.

He was being treated in hospital for injuries to his eyes and face, and police were investigating whether the attack was related to his work, said Jakarta police chief Mochammad Iriawan.

It was not the first time Baswedan had been attacked and his agency said it would not be cowed.

“We strongly condemn the uncivilized attack on Novel. Novel is us and we are the KPK. We will never stop fighting against corruption,” the KPK said in a statement.

Deputy agency chief Laode M. Syarif said police would be asked to step up security for agency officials.

“We will ask the national and city police for extra protection for KPK investigators,” he told reporters.

President Joko Widodo ordered police to investigate and urged KPK officials to be vigilant.

“This is a brutal act that I strongly condemn,” Widodo told reporters at the presidential palace. “All investigators must be alert and keep working hard.”

Two suspects on trial over the graft case have told a court that at least 37 politicians benefited from the theft of funds from the ID procurement budget, including parliament speaker Novanto.

PARTY PAYMENTS?

Late on Monday, the KPK banned Novanto from going overseas for six months.

A KPK public relations official, Ipi Maryati, said Novanto had been banned from travel so that “whenever his information is needed in the investigation of the case, he’s not out of the country”.

Novanto, who is also the chairman of Indonesia’s second-biggest political party, Golkar, told media he would cooperate with authorities. He has not been charged and has previously denied wrongdoing.

Golkar’s secretary general, Idrus Marham, told Reuters the party and Novanto would respect the legal process.

“We also believe in the principle of innocent until proven guilty,” Marham said.

The allegations against Novanto and others, set out in a KPK indictment, include accounts of sums ranging from $5,000 to $5.5 million being divided up in a room in parliament among members of various parties, including the one backing President Joko Widodo.

The president’s party has said previously it was investigating the accusation and would follow the legal process.

Global anti-graft watchdog Transparency International found in a recent survey that Indonesians perceived parliament to be their most corrupt institution.

Four years ago, the KPK had to call for support from the public to protect its headquarters after police tried to barge in to demand Baswedan be handed over to them. At the time, he was investigating police corruption.

Baswedan had also in the past been the target of an attempted hit-and-run, Maryati said.