BBC News with Mike Cooper

The International Monetary Fund and the European Commission have promised to act swiftly after Greece said it needed to activate a 60-billion-dollar rescue package agreed in principle last week. Correspondents say the IMF is likely to demand tough austerity measures. The crisis sparked an angry skirmish in Athens this evening as Malcolm Brabant reports.

The authorities here are on alert for social unrest. Seasoned left-wing political activists acknowledge that 24-hour strikes and frequent demonstrations have failed to persuade the government to water down its austerity programme. "What we need," said one activist, "are open-ended strikes on occupations of factories and other places of employment." The Socialist government has made it clear that it won't tolerate repeat of the riots of 2008 when city centres across the country were vandalized and buildings burned. The police have been ordered to be more robust with troublemakers.

Governor of the American state of Arkansas Jan Brewer has signed into law a bill tightening immigration hours after President Obama criticized it. The unprecedented state law gives new powers to local police to question people about their immigration status. Governor Brewer said the law would strengthen border controls in the state which neighbors Mexico. President Obama called the measure misguided and said he had instructed the Justice Department to investigate whether it violated the civil rights of Latinos and other immigrants.