The Malaysian Anti-Corruption Commission (MACC) said it arrested Rosmah, 66, who will face charges in court on Thursday for infringing an anti-money laundering law.

"Rosmah will face several charges," the agency said in a statement.

Rosmah's arrest follows three rounds of questioning by anti-graft agents over state fund 1Malaysia Development Berhad (1MDB), from which U.S. authorities say more than $4.5 billion was misappropriated. Last Wednesday, she was questioned for nearly 13 hours.

After Najib's election defeat in May, the couple has seen their world turned upside down, with authorities banning them from leaving the country and the police searching their homes.

Read: Malaysian Anti-graft Agency to Question Wife of Najib

Malaysians have been outraged by the seizure of around $275 million worth of cash and goods, including a vast collection of Hermes Birkin and other designer handbags, jewelry and watches from properties linked to the couple.

Najib has said most of the seized items were gifts to his wife and daughter and had nothing to do with 1MDB.

The anti-graft agency did not say if the charges against Rosmah relate to 1MDB.

After the arrest, Rosmah's lawyer, Geethan Ram Vincent, told reporters her lawyers had not been informed of the nature of the charges to be filed against her.

Rosmah smiled and shook hands with officers of the anti-graft agency as she arrived at its headquarters at around 0300 GMT, wearing a headscarf, and traditional Malay garb of a floor-length skirt and a blouse in lime-green.

She made no comment to reporters.

Read: Malaysia's Najib Razak Charged with Money Laundering

Najib faces 32 charges ranging from money laundering to abuse of power and criminal breach of trust in the effort to uncover how billions of dollars went missing from 1MDB.

He has consistently denied wrongdoing and has pleaded not guilty to all the charges.

Najib, 64, himself faced questioning on Wednesday by the anti-money laundering and anti-terror financing division of Malaysia's police over a money-laundering inquiry, media said.

He is also set to be in court on Thursday for a pre-trial hearing of charges related to 1MDB filed against him.

Corruption accusations have dogged Najib for years and came to a head in 2015 when the Wall Street Journal reported that nearly $700 million in 1MDB funds was diverted to his personal bank account.

Najib lost the May election to his one-time mentor Mahathir Mohamad, who swiftly reopened a probe into 1MDB.

REUTERS