By Sarah Marsh and Andreas Rinke BERLIN (Reuters) -Cables vital for the rail network were intentionally cut in two places causing a near three-hour halt to all rail traffic in northern Germany on Saturday morning, in what authorities called an act of sabotage without identifying who might be responsible. The federal police are investigating the incident, Interior Minister Nancy Faeser said, adding the motive for it was unclear. The disruption raised alarm bells after NATO and the European Union last month stressed the need to protect critical infrastructure after what they called acts of sabot…