A regional court in Muntinlupa, a suburb of Manila, issued a warrant for the arrest of Leila de Lima on Thursday. The order comes less than a week after illegal drug charges were filed against the opposition senator.

Judge Juanita Guerrero said she found "sufficient probable cause" in the allegations against de Lima after "careful evaluation of the ... information and all the evidence presented" by state prosecutors.

De Lima's lawyer, however, contested the order's credibility, saying it is anchored in insufficient evidence.

"We are really disappointed by the issuance of the warrant," Alex Padilla said. "The court made the decision based on nothing."

The charges come from allegations made by national penitentiary inmates. They claimed to have paid de Lima millions of pesos while she was justice minister so they could continue trading drugs in prison.

Duterte's most outspoken critic

De Lima has openly condemned Duterte's administration since the controversial leader took office last June. Duterte, 71, won the federal election after pledging to eradicate drugs in the Philippines by killing tens of thousands of drug dealers and users.

More than 7,000 people have been killed since June, 2016

More than 7,000 people have died in police operations and alleged extrajudicial killings since Duterte launched his so-called drug war immediately after his inauguration.

Last August, de Lima, the former head of the Senate Committee on Justice and Human Rights,launched a senate inquiry into alleged extrajudicial killings under Duterte's administration. A month later, she was stripped of her appointment.

Duterte pledged to eradicate drugs from society by killing users and dealers

The 57-year-old senator has been one of Duterte's most outspoken critics.

"We can certainly deal with the drug issue without killing people or at least keep the casualties to a minimum," she told DW in August.

Grounds for impeachment

In December, de Lima said the president's anti-drugs campaign and alleged vigilante killings were "a betrayal of public trust".

"That constitutes high crimes because mass murders certainly fall into the category of high crimes," she said. "High crimes is a ground for impeachment under the constitution."

Political persecution

De Lima has dismissed the charges as an attempt to intimidate Duterte's critics. The opposition legislator denied the accusations, calling them "plain and simple political persecution” for her opposition to the president's drug war.

According to Senator Risa Hontiveros, de Lima is currently holed up in her Manila office. While she has yet to be arrested, Padilla said a hearing on the case had been scheduled on Friday.

mcm/sms (dpa, AP)