The Philippines hit out Friday at "foreign interference" after European lawmakers demanded the release of a top critic of President Rodrigo Duterte who was arrested last month on drug charges.
Senator Leila de Lima has been detained at national police headquarters since her arrest on charges that she and rights groups insist were manufactured to end her campaign against Duterte's deadly drug war.
"We remind everyone, including international bodies, to allow us to deal with our domestic challenges without unwarranted foreign interference," presidential spokesman Ernesto Abella said.
"While some may feel a 'sovereign obligation' to step into the affairs of another state, it is vital to recognise that the Philippines is a sovereign state."
Abella insisted that De Lima was arrested on criminal, not political charges, and that she was being treated fairly in the court system.
European lawmakers on Thursday urged the Philippines to release De Lima, a former human rights commissioner who had also sought to expose Duterte as the leader of death squads when he was mayor of southern Davao city.
The European Parliament resolution on Thursday also condemned "the high number of extrajudicial killings by the armed forces and vigilante groups related to the anti-drug campaign".
Duterte, who took office in the middle of last year, has overseen a ruthless campaign to eradicate illegal drugs that he says are threatening to turn the Philippines into a narco-state.
Police have reported killing more than 2,500 people, while rights groups say there have been more than 5,000 other deaths linked to the drug war.
Amnesty International and Human Rights Watch have warned Duterte may be overseeing crimes against humanity, and have accused police of running anonymous death squads.
Duterte easily won last year's elections after promising tens of thousands of people would die in the drug war, and has as president repeatedly called for addicts as well traffickers to be killed.
But Duterte and his aides also insist security forces are not breaking any laws, and are not carrying out extrajudicial killings.
"We reiterate that the Duterte administration does not engage in so-called extrajudicial killings. It continues to follow due process and holds itself accountable for its actions," Abella said Friday.
De Lima released a statement on Friday saying she was "deeply heartened" by the European Parliament resolution.
"It's not at all an interference with our country's internal affairs but rather an aggregate assertion of the universal values of truth, justice and humanity," she said.