MANILA - The Philippine Center for Investigative Journalism (PCIJ) on Friday said its websites were targeted by cyber attacks following its pieces on the Duterte administration's campaign against illegal drugs.

"There has been an attack on our websites, www.pcij.org and www.pcij.org/blog. This is the reason why our sites are not accessible at this time," PCIJ said in a Facebook post.

"The attack follows the publication of PCIJ reports on the drug war of the Duterte administration, and our 'Know Your Rights' advisories for citizens," the media group added.

PCIJ also tweeted: "A phrase with explicit curse and threat has been written by the attackers into our stories on the drug war of the Duterte Administration."

A visit to PCIJ.org and PCIJ.org/blog shows a 404 error page.