BERLIN (REUTERS) - Nearly 300 people are facing prosecution in Germany for supporting ISIS (Islamic State in Iraq and Syria), German Justice Minister Heiko Maas has said, adding that it was a sign that anti-terrorism laws were working and tougher legislation was not needed.

"Whoever supports IS can already be prosecuted under existing laws," he told Sunday's weekly newspaper Welt am Sonntag in an interview, using a short form for ISIS, after some politicians called for tighter laws. He added, however, that he would present a draft law by the end of the year to tackle the flow of money to ISIS.

On Friday, a state prosecutor demanded a prison term of more than four years for a 20-year-old German man accused of fighting with ISIS insurgents in Syria. It is the first trial of its kind in Germany and dozens more are due to begin in coming months.

ISIS has captured swathes of territory in Syria and Iraq, massacred many non-Sunni Muslims, beheaded some Western prisoners, and declared a caliphate ruled under sharia, or Islamic law, in the heart of the Middle East.

Thousands of Western volunteers have travelled to Syria and Iraq to join militant groups. Law enforcement authorities are cracking down on returning fighters, amid fears of attacks.

Security authorities say about 550 German citizens have joined ISIS and about 60 have been killed, some in suicide attacks. Around 180 are believed to have returned.

In September, Germany introduced a ban on ISIS that outlawed propaganda, the display of symbols and activities linked to the group.

Some of those facing prosecution are accused of supporting ISIS by raising funds or helping supply equipment from Germany.