Greek Killing Raises Fears of Extremism ATHENS - European officials expressed concern on Thursday about a rise of extremism in Greece, a day after thousands of demonstrators took to the streets in several Greek cities to protest the killing of an antifascist activist. The Greek police said the killer was a supporter of the right-wing Golden Dawn party. Thorbjorn Jagland, the secretary general of the Council of Europe, said "an extremely dangerous development" was emerging in Greece and in other parts of Europe. "Sections of society are becoming more radicalized, and there is a real risk that hate speech turns into violence and coldblooded murder," he said. Prime Minister Antonis Samaras of Greece made another appeal for calm on Thursday, describing the killing of the activist - Pavlos Fyssas, 34, a leftist hip-hop singer - as "inhuman." He said the government was "determined not to allow the descendants of the Nazis to poison our social life, to commit crimes, to terrorize and to undermine the foundations of the country that gave birth to democracy." Mr. Samaras did not say what actions the government would take, and did not comment on a suggestion advanced by the country's public order minister, calling for changes in the laws defining criminal organizations to rein in Golden Dawn. The minister late on Thursday sent the Supreme Court prosecutor a list of offenses believed to have been carried out by Golden Dawn and asked for the party to be treated as a criminal organization. The party, whose members have been accused of criminal violence against immigrants, has gained popularity recently, especially among Greeks angered by high unemployment and economic woes. Golden Dawn has insisted that it had nothing to do with the killing of Mr. Fyssas. Tensions have been growing between Mr. Samaras's fragile coalition government and the main leftist opposition party in Greece, Syriza, which has also been gaining in popularity. One of the prime minister's chief advisers, Chrysanthos Lazaridis, said Syriza was also engaged in political violence, and suggested that the leftist party was not part of Greece's "constitutional axis." Mr. Samaras said, "Political disagreements should be solved with democratic dialogue, not inflammatory arguments or with violence, wherever it may come from."