Several thousand demonstrators chanted Islamic slogans after Moslem prayer services today, and authorities reported 900 arrests and an unspecified number of deaths in three days of rioting. Police and troops were blocking the demonstrators, estimated by reporters to number at least 6,000, in the Belcourt district in eastern Algiers. They chanted ``God is Great'' and other slogans and called for establishment of an Islamic republic. Earlier today, Algerians formed long lines for bread after an overnight curfew that was almost universally obeyed. On Thursday, the government declared a national state of emergency and put all police and administrative authorities under the military. Occasional gunshots broke the early morning silence. It was not clear whether the shots were fired at protesters or were warnings to chase away the few people in the streets. Protesters this week have included youths protesting an austerity program that has sharply increased prices, Islamic fundamentalists who oppose the government's secular orientation and rioters whose political stance was not known. The military command said 900 people were arrested in the three previous days and were caught ``red-handed in pillage and vandalism.'' In a separate statement, the command said street battles caused ``losses of human life among the demonstrators as well as in the ranks of the forces of order.'' It said the deaths occurred Thursday during the day and night. It did not say where in Algiers they happened. More than 30 people seriously injured in the clashes were admitted to Mustapha Hospital in Algiers, medical sources said today on condition of anonymity. They said the worst injuries occurred Wednesday night. President Chadli Bendjadid proclaimed a state of emergency on Thursday and ordered a curfew from midnight to 6 a.m. The army was given responsibility for public order for the first time since Algeria won independence from France 26 years ago. Bakeries were among the few shops open today, as other food stores remained closed either for lack of supplies or for fear of renewed violence. While prices of meats and other goods have soared, bread remains heavily subsidized by the government. Army convoys escorted trucks carrying flour to bakeries early in the morning to assure supplies. ``Getting provisions to the citizens is one of our main concerns, along with security,'' an army officer on one of the escorts told The Associated Press. He declined to give his name. The national airline Air Algerie announced today it was canceling all its flights, but international airlines continued to operate flights in and out of Algiers' Houari Boumediene airport. Government offices and other businesses were closed as usual today, the Moslem day of prayer. Former President Ahmed Ben Bella, who lives in exile in Geneva, was quoted in the Paris daily Le Figaro as saying some people were killed in the disturbances, without specifying how many or providing details. ``It was predictable that young people would rise up against the corruption, the bad management and the total lack of freedom,'' Ben Bella, who was president from independence in 1962 until he was overthrown in a military coup in 1965, was quoted as saying. The French news agency Agence France-Presse reported that two brothers, aged 14 and 23, were killed in the El-Biar neighborhood and quoted a relative as saying she saw their bodies at the Birtraria hospital. A hospital official, refusing to identify himself, denied the report today. The protests began last week with a series of strikes in industries _ which are nearly all government-controlled _ as well as the postal and telephone service and Air Algerie. By unofficial estimates, unemployment is above 40 percent in the capital. Under the government's economic reform program, prices for basic food staples other than bread have risen sharply. Slightly more than two pounds of beef sell for $25 or more.