A court in the Philippines has ordered the arrest of Leila de Lima, an opposition senator and a leading critic of President Rodrigo Duterte, over illegal drug charges.

De Lima, a vocal opponent of Duterte's bloody anti-drug campaign, is accused of orchestrating a drug trafficking ring when she was justice secretary during the 2010-2015 administration of Benigno Aquino.

Warrants were also issued on Thursday for the arrest of the former head of the prison agency as well as a de Lima aide, who is accused of accepting bribes on behalf of the senator.

De Lima has denied the charges, calling herself a victim of political persecution and saying she has long prepared herself to be the first "political prisoner" under the Duterte administration.

In a press conference on Thursday, de Lima said that she will await her arrest at the Senate on Friday.

"While the issuance of the warrant of arrest is questionable, I do not have any plans to evade it," she said, calling the order premature as the court has yet to hear the response from her lawyers.

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Duterte, 71, won a presidential election last year after promising during the campaign to eradicate drugs in society by killing tens of thousands of people.

Since his inauguration on June 30, an anti-drug drive has seen more than 7,000 people killed over suspected drug links - with more than 60 percent of the deaths carried out by unknown assassins.

De Lima has previously called for foreign intervention to put an end to the "state-inspired" extrajudicial murders, which she said have been instigated by Duterte since his election to power.

De Lima also led a series of Senate investigations over allegations that police officers were involved in the killings, and that hired killers were operating under orders from police.

Trumped up charges

De Lima's supporters also insist that she is innocent, and that the charges are trumped up to silence one of Duterte's most prominent critics.

In a statement to Al Jazeera, Senator Paolo Aquino condemned the "political persecution" of his fellow opposition Senate member.

"This arrest is purely political vendetta and has no place in justice system that upholds the rule of law. This is condemnable.

"We reiterate that an arrest based on trumped-up charges is illegal," he said citing the "haste" in de Lima's arrest.

De Lima previously claimed that she was targeted because of her criticism of Duterte's drug war policy.

During her time as head of the country's human rights body, de Lima also led the investigation into the alleged extrajudicial killings of an estimated 1,000 drug suspects in Davao, while Duterte was mayor of the city.

When Duterte won as president in 2016, his feud with de Lima continued.

At one point he called on her to "hang herself", after he ordered prosecutors to investigate the senator's alleged links to the drug syndicate.

This week, de Lima branded the president a "sociopathic serial killer" after new allegations surfaced accusing Duterte of ordering drug killings in Davao.