The French premier has announced tightened controls on immigration, part of his government's response to the country's worst civil unrest in four decades. Legal immigrants who ask for a 10-year residency permit or citizenship should show that they have integrated and mastered French, Prime Minister Dominique de Villepin said Tuesday. France also plans to crack down on fraudulent marriages that some immigrants use to acquire residency rights and launch a stricter screening process for foreign students, Villepin said. Anti-racism groups widely opposed the measures, saying that greater government scrutiny of immigrants could stir up racism and racist acts. Both Villepin and Interior Minister Nicolas Sarkozy have announced law-and-order measures since the rioting broke out this month in depressed suburbs where many immigrants live. Marriages celebrated abroad between French people and foreigners will no longer be automatically recognized in France, Villepin said. Consulates must screen couples first before foreign partners can be granted French identity papers, he said.