German security forces are investigating whether the alleged Islamic terrorist bombing plot they say was foiled this week involved an international network of at least 10 people, including foreign nationals.

A spokesman for Monika Harms, the federal prosecutor, told the Financial Times she was investigating seven people to establish if there were links to the three men arrested on Tuesday in western Germany on charges of planning car bomb attacks against US-related sites in the country. Five of those being investigated were known by name, he added.