VIENNA, Austria - Austria's interior minister, wading deeper into an increasingly acrimonious immigration debate, said Tuesday he wants to double the time that immigrants spend in German language courses to ensure they are assimilated into Austrian society.

Guenther Platter told public broadcaster ORF he thinks the current requirement of 300 hours of German instruction is not enough and should "at least be doubled."

Several other European countries, including Denmark and the Netherlands, require immigrants to learn the local language, but only Austria mandates basic proficiency for foreigners seeking a residency permit.

Platter and other advocates contend the language courses - mandated by law since 2003 - are key to ensuring that immigrants integrate into society rather than form ethnic enclaves.

Under that law, immigrants who refuse to take the courses are subject to expulsion.

Platter came under fire last month for expelling a well-integrated Kosovo family that had lived in Austria since 2001 and spoke fluent German.

When one of the daughters, 15-year-old Arigona Zogaj, fled into hiding and later released a video in which she tearfully threatened to kill herself, the case touched off a nationwide debate.

Arigona's father and four siblings were not deported under the language law, but under tightened residency guidelines. Authorities ruled there was no proof they would face persecution if returned to Kosovo.

About 500 demonstrators protesting the government's deportation policy marched through central Vienna on Tuesday, carrying banners that read "Residency rights for all" and "Fight racism."

Arigona, who is now in the care of a Catholic priest, returned to school on Tuesday for the first time in several weeks, after Platter assured her she would not face surprise deportation.

Her Austrian classmates greeted her with hugs, a bouquet of flowers and homemade cards cut in the shape of hearts.

On Monday, the government set up a special commission that will review Austria's immigration and asylum policies and report back to parliament by mid-2008 with suggestions for improvements.