VIENNA (Reuters) - Austrian authorities watched a meeting in Vienna this summer between foreign Islamists and the jihadist who killed four people last week, and trailed him for days but then stopped, news agency APA reported on Monday.Austria has acknowledged that “intolerable mistakes were made” in the handling of intelligence on the attacker, a convicted jihadist, who killed four people in a shooting rampage in the centre of Vienna last Monday. He was shot dead by police. First Vienna said it had mishandled information from Slovakia that the gunman had tried to buy ammunition there in July. Then it admitted he had met people from Germany who were under observation there and who travelled to Austria, and that could have led it to see him as a greater threat. On Monday it confirmed a report by Swiss newspaper NZZ am Sonntag that he had also met two Islamists arrested in Switzerland in connection with the attack who had travelled to Vienna between July 16 and July 20.