BERLIN (AFP) - The cupola on Germanys Reichstag parliament building was closed until further notice to visitors on Monday after media reports said the popular tourist site was a target for extremists. In a statement the parliament gave no reasons for the closure, which also covers the historic buildings roof terrace. Pre-arranged group visits were still allowed, however. Last week German authorities beefed up security at crowded places such as airports and train stations after Interior Minister Thomas de Maiziere said that Berlin had received a tip-off that attacks were being planned in Germany.