Influential former Malaysian premier Mahathir Mohamad and some key ruling party members demanded Monday that embattled Prime Minister Najib Razak answer a barrage of corruption allegations.
On the same day, a whistle-blower and his lawyer detained for their efforts to expose graft allegations against Najib were charged with attempting to "sabotage" the country's banking sector.
Critics want Najib to explain massive sums allegedly missing from state-owned development company 1MDB which he launched, as well as the revelation in July that nearly $700 million in mysterious transfers had been made to his personal bank accounts.
"Unless somebody speaks up, the government will get away with doing all kinds of wrong things," Mahathir told a press conference, according to The Star newspaper.
"So they may take action against me or any one of us but somebody has to take the risk to voice our disquiet, anger and feeling that the government is not looking after the interests of this country."
Joining Mahathir, Malaysia's leader from 1981-2003, at the press conference were several heavyweights from the ruling United Malays National Organisation (UMNO), which has held power since 1957, including party deputy president and the country's former deputy premier, Muhyiddin Yassin.
Muhyiddin who has repeatedly called for Najib to shed light on the corruption allegations, was stripped of his deputy premier title by Najib in July.
Both Najib and 1MDB vehemently deny any wrongdoing.
'Line in the sand'
Tensions have been simmering in UMNO ranks since allegations of corruption surrounding Najib and 1MDB surfaced in July, Ibrahim Suffian, head of the Merdeka Center polling firm, told AFP.
"This is a confluence of different strands of dissent within UMNO coming together," he said.
"A line has now been clearly drawn in the sand -- them on one side and Najib on the other -- and the first salvo has been fired."
Last week Malaysia's nine state sultans, in a rare statement, said failure to investigate the allegations against Najib had created a "crisis of confidence". They called for a probe to be revived.
Inquiries have stalled after Najib fired his attorney-general in July and after police raided the anti-corruption agency offices in August.
Malaysia's central bank said it had formally recommended criminal proceedings be launched against 1MDB in August but the recommendation has since been dismissed by a Najib-appointed attorney general.
Mahathir and others at the press conference also condemned the detention of the whistle-blower and his lawyer.
Khairuddin Abu Hassan, a former UMNO member, was arrested in September after launching an international campaign to expose the allegations.
His lawyer Matthias Chang was arrested last week for suspected involvement in the campaign.
Facing the possibility of 15 years in jail if found guilty, they were charged on Monday with attempting to "sabotage Malaysia's banking and financial services sector", The Star and the New Straits Times reported.
Regulators in the United States and elsewhere are now reportedly looking into the affair, with authorities in Switzerland and Singapore saying they had frozen some accounts as they probe possible money-laundering and other crimes.
Najib's allies say the money deposited into his accounts was "political donations" from Middle Eastern sources, but have refused to provide details.