SANTIAGO: Bolivia's former President Jeanine Anez began a four-month jail term on Monday as investigators probe allegations she helped in a coup that led to the removal of longtime leader Evo Morales from power in 2019.

The arrest of the conservative interim leader - who was in power for less than a year after the ouster of leftist icon Morales - has sparked sharp criticism from human rights groups and the Organization of American States (OAS), who say judicial channels are being abused for political ends.

"They have become repressive instruments of the ruling party," the OAS said in a statement on Monday. "Bolivia's judicial system is not in a position to provide the minimum guarantees of fair trial, impartiality and due process."

Anez, who was taken into police custody following a raid on her home in the north-central city of Trinidad early on Saturday, was transferred to a women's prison in the highland administrative capital La Paz on Monday.

Prosecutors for the socialist government, which returned to power in October, said she used security force allies to push Morales to resign after contested elections and eventually install herself as interim president.

Anez has rejected the charges against her as political persecution and insisted she took part in a constitutional succession to replace Morales.

Her former energy and justice ministers have also been ordered into custody on charges of terrorism, sedition and conspiracy over the alleged coup. Arrest warrants have also been issued for community leaders and former military and police chiefs.

Justice Minister Ivan Lima said on state television late on Sunday he would seek a 30-year jail sentence for Anez if she were found guilty and flagged other suits against her, including over a $350 million loan from the International Monetary Fund.

The OAS, which was an official monitor of the 2019 election and had found it fraudulent, called for the release of Anez and her ministers and an impartial international investigation.

Amnesty International said in a statement that Anez's arrest, coupled with a decision to throw out any pending cases against members of the ruling socialist party, represented the continuation of a decades-long "crisis of impunity" in Bolivia.

Pablo Gutierrez, the prosecutor in charge of the case, insisted his team had followed the letter of the law and that it was not about political persecution.

Anez, 53, a former center-right senator, took power after Morales resigned amid widespread violent protests and claims backed by international organizations, including the OAS, that he fraudulently won the October 2019 election.

At least 33 people were killed in the violence that followed the election, the majority of them after Anez took office.

On Monday, the former commander of Bolivia's army, General Jorge Pastor Mendieta, voluntarily appeared at the prosecutor's office and was detained.

Mendieta's lawyer, Zuleika Lanza, said the former commander was not officially wanted, but had learned through the media that he was being investigated.