The Judicial Department said it was necessary to solve the case urgently. It did not comment further. The Danish newspaper Berlingske quoted the family as saying the man was a Danish citizen but had spent his childhood in Saudi Arabia. He was in Lebanon for a short holiday. The family did not wish to be identified. Responding to a request for comment from Reuters, a spokesman for Denmark's foreign ministry said it had been informed by Saudi Arabia of the arrest of a Danish citizen. "We take this case very seriously and are in close contact with the Saudi Arabian authorities," he said. Senior Saudi Arabian officials told Reuters the person was a 28-year-old Saudi national who had been studying in Denmark on a student visa. He was arrested for "criminal behavior" and was being questioned by police. Suicide bombers killed at least 235 people in attacks on Shi'ite Muslim mosques in Saudi Arabia on May 22, one of the worst such attacks to target the religious minority in the kingdom.