Interior Minister Thomas de Maiziere on Monday cautioned Germans against indiscriminately branding all refugees a security threat after a rash of attacks over the last week. "We must not place refugees under general suspicion despite individual cases that are under investigation," he said in an interview with the Funke media group after a string of assaults in southern Germany, some involving asylum-seekers. Chancellor Angela Merkel's deputy spokeswoman Ulrike Demmer later expressed the government's "shock" after the rash of violence over the last week but also warned against labeling all refugees. "Most of the terrorists who carried out attacks in recent months in Europe were not refugees," she said. "This fact corresponds with ongoing investigations indicating that the terrorism threat (among refugees) is not larger or smaller than in the population at large." Authorities said a man who set off a bomb late Sunday near a music festival in the southern town of Ansbach, killing himself and wounding a dozen others, was believed to be a 27-year-old Syrian refugee. He was facing imminent deportation to Bulgaria, where he was first registered as an asylum seeker, an interior ministry spokesman said. Regional officials had said a terrorist motive was "very likely" but a spokesman for the federal interior ministry said there was as yet "no credible evidence" of a link to extremism. Earlier in the day, a Syrian refugee, 21, had killed a 45-year-old Polish woman with a large kebab knife in the southwestern city of Reutlingen in what police said was likely a "crime of passion." The two attacks came as Germany was already reeling from a shooting rampage in Munich on Friday by an 18-year-old German-Iranian who killed nine people before turning the gun on himself. And last Monday, another teenager, wielding an ax and a knife, wounded four passengers on a regional train, before injuring a passer-by as he fled police. The assailant, who was shot dead by authorities, was registered as an Afghan asylum seeker but may have in fact been Pakistani. He had no criminal record but authorities believe he may have been "self-radicalized" and inspired by Daesh (the so-called IS), which later claimed responsibility for the attack. Meanwhile a news report claimed that Germany's federal criminal police have 410 leads on possible terrorists among refugees here, a local newspaper reported on Monday. The Neue Osnabruecker Zeitung newspaper said that compared with 369 leads in mid-May since the beginning of the migrant crisis last year. Investigations have been launched in 60 cases, the newspaper said. It cited federal BKA police as saying they did not currently have any concrete indications of attack plans. "In view of continuing migration to Germany we must assume that there could be active and former members, supporters and sympathizers of terrorist organizations or Islamist-motivated war criminals among the refugees," the newspaper quoted federal police as saying. In another development, a 16-year-old Afghan youth who was arrested on Sunday had been in contact via WhatsApp with an 18-year-old gunman who killed nine people in Munich two days earlier and also met him just before the attack, Bavarian officials said. The youth, who was questioned after he contacted police following the shooting, is under investigation for possibly having failed to report the plans of the gunman. Thomas Steinkraus-Koch, senior public prosecutor in Munich, told a news conference on Monday the Afghan had been in contact with the gunman via WhatApp until shortly before the attack. He wiped the conversation, but officials were able to retrieve it. "This (WhatsApp) chat and questioning of a suspect has shown that the Afghan met the gunman directly before the gun attack at what was later the scene of the crime," Steinkraus-Koch told a news conference in Munich. The WhatsApp chat showed the Afghan knew the German-Iranian gunman was in possession of a Glock 17 firearm, Steinkraus-Koch said. "They got to know each other last summer, in 2015, in a psychiatric clinic where they underwent treatment," he said. "There, it also became apparent to the (Afghan) suspect that the attacker was interested in Breivik," Steinkraus-Koch added, referring to Anders Breivik, who killed 77 people in back-to-back attacks in Norway in 2011. The Afghan's decision to delete his WhatsApp chat with the gunman and their meeting just before the Munich attack led investigators to suspect he knew of the planned shooting in advance.