GENEVA, Switzerland—The Press Emblem Campaign (PEC), set up to push for an international treaty to protect journalists, on Tuesday condemned the political massacre in southern Philippines that left 12 reporters dead.

"This crime against humanity, that surpasses all imagination, underscores the repeated calls of the PEC for an additional protocol or convention to protect journalists," said the Geneva-based group established by journalists alarmed at the rising death toll among media workers worldwide.

Gunmen allegedly hired by a local political chief abducted then shot dead a group of politicians from a rival clan and accompanying journalists traveling in the southern province of Maguidanao on Monday.

The latest death toll stood at 46, including at least 12 journalists.

"It is a horrifying development in the inability to protect civilians as well as journalists and gives strength to the arguments of the PEC to clarify the Geneva Conventions... reinforcing them in the face of new threats and dangers," said the PEC, which condemned the attacks in the "strongest possible manner."

It called for an "urgent investigation" into the massacre, asking the UN Human Rights Council for a "quick response."

"This is a massacre that requires a quick response from the Human Rights Council, because it has surpassed all limits acceptable in international humanitarian law, it is of an unprecedented scale that crosses all borders," it said.

The massacre brings the number of journalists killed this year to 88, said the PEC.

Before the massacre, the New York-based monitor Committee to Protect Journalists ranked the Philippines as the fourth deadliest country for journalists in terms of reporters' deaths for 2009.

However Monday's killings will see the Philippines leapfrog Somalia, Iraq, and Pakistan into the top spot