US Secretary of State Marco Rubio has cited the fatal firebombing attack on the home of a Greek governing party politician as he urged representatives from more than 60 countries to step up efforts against what he described as a resurgence of far-left political terrorism.

Speaking at the opening of a State Department summit attended by roughly 65 foreign delegations on Thursday, Rubio referred to the attack earlier this month on the Thessaloniki home of New Democracy parliamentary candidate Afroditi Nestora, in which her 72-year-old mother, Vagia Nestora, suffered severe burns and later died.

“Two weeks ago a 72-year-old woman was burned on over 80 percent of her body in her own home in Greece and she died, executed by a fire bomb because her daughter dared to stand for office,” Rubio said.

Rubio argued that governments had spent too long overlooking what he called a resurgence of transnational far-left extremist violence and urged greater international cooperation to confront the threat.

He described radical leftism as “a poisonous resentment cloaked in the language of equality and justice.”