Greek students storm news show on state TV

Protesters forced their way into Greece's state NET television news studio and interrupted a news broadcast featuring the Prime Minister so they could urge viewers to join mass anti-government demonstrations.

For more than a minute, about 10 youths blocked a broadcast showing a speech by Prime Minister Costas Karamanlis. Instead, they displayed banners reading: "Stop watching, get out on to the streets," and "Free everyone who has been arrested". No one was hurt, and no arrests were reported.

The NET chairman, Christos Panagopoulos, said the protesters forced their way violently into the studio. "This goes beyond any limit," he said.

It was the latest twist in 11 days of riots and protests after a policeman shot and killed a 15-year-old boy on 6 December. The protests have evolved from being just aimed at Greek police to being highly critical of Mr Karamanlis' conservative government. He has rejected mounting demands to resign and call new elections.

Earlier yesterday, masked youths attacked riot police headquarters in Athens and protesters clashed with police in the northern city of Thessaloniki. The disturbance there followed a court decision that found eight police officers guilty of abusing a student after riots two years ago. In Athens, police said 30 young people threw petrol bombs and stones at the riot police building, causing extensive damage to seven cars and a police bus. Students blocked streets in Athens and dozens of teenagers gathered outside the capital's main court complex and a maximum security prison – where some threw stones at police. Protesters have called for riot officers to be pulled off the streets, for police to be disarmed and for the government to revise economic, social and education policies.

The protests have brought higher education in Greece to a standstill. And lessons have stopped at more than 100 secondary schools that are under occupation by students, according to the Education Ministry. Scores of university buildings are also being occupied.

After the death of Alexandros Grigoropoulos, 15, youths smashed and burnt hundreds of shops in Athens' main shopping area, and attacked riot police who responded with large bursts of tear gas. Dozens of people have been injured, while more than 300 people have been arrested. The policeman accused of killing the teenager has been charged with murder and is being held pending trial.