Berlin - German anti-terrorism police on Friday arrested two men in Berlin suspected of recruiting fighters and supplying cash to the Islamic State extremist group in Syria.Officials named one of the suspects as Ismet D, aged 41. The other man was also in his 40s. Three other suspects were questioned and then released by police, who said their acts were not grave enough for them to be remanded in custody.Berlin's city prosecutor Martin Steltner told dpa that Ismet had taught a course on Islam at a Berlin mosque and had "radicalised" at least 30 people and prepared them to go to the civil war zone in Syria to fight "infidels."Ismet, who called himself the "emir" of the Berlin group, had himself been planning to visit Syria, police added."We found and confiscated airline tickets during the search," said police spokesperson Stefan Redlich."The investigations have been under way for a year. This round-up itself has been in planning for a long time," Redlich said, adding there was no evidence the group were planning attacks in Germany.Steltner described the cell as a terrorist logistic-operations unit, which recruited for and organised travel to Syria. The other three suspects were "subsidiary participants" who had supplied night-vision goggles, money and air tickets for the travellers.Another man who was arrested the previous evening in a separate inquiry in the western industrial city of Wolfsburg was remanded in custody on Friday by a federal judge, prosecutors announced.Police said that 26-year-old man of Tunisian origin was accused of having joined the Islamic State (ISIS) movement and having undergone military training during a three-month stay in Syria, but was not suspected of plotting any attack in Germany.Abstract threatIn Berlin, Interior Ministry spokesperson Tobias Plate refused comment on whether the arrests had been internationally co-ordinated.He said several countries had been in "close exchange" on security matters before the terrorist attacks in France last week.Plate said Germany had perceived a high level of "abstract threat" from international terrorists for months, adding, "From the point of view of the ministry, nothing prompts any alteration in the estimation."Berlin state's minister of the interior, Frank Henkel, said the arrests were not connected to the attacks in France last week.German authorities said this week that 600 residents of Germany were believed to have so far travelled to the war zone in Syria and Iraq to join the Islamist militants there. Some of the 600 had since returned home.A total of 250 officers and three commandos were involved in the Berlin operation in central-city neighbourhoods.