Germany's development aid minister, Gerd Mueller, has accused Qatar of financing the Islamic State terror group.

"A story like this always has a history," Mueller said in an interview with public broadcaster ZDF. "Who is financing these troops? Hint: Qatar."

German Vice-Chancellor and Economy Minister Sigmar Gabriel has called for a "debate" about who has been financing the terror group, which has created an Islamic "Caliphate" which straddles the Iraq-Syrian border.

The country is still to decide whether it should support Iraqi Kurds, fighting the jihadists, with lethal or non-lethal military aid, a controversial issue because of its historic involvement in two world wars.

There are also links between Qatar's winning the 2022 World Cup bid and the Islamic State group. The country's rich Aspire sports academy collaborated on a series of religious lectures in Doha during Ramadan this year which included the Saudi cleric Mohammad al-Arefe.

Arefe has been banned from the United Kingdom by the Home Office for appearing at a Cardiff mosque where three teens were allegedly radicalised, going on to join the terror group.

Aseel Muthana, Nasser Muthana and Reyaad Khan were all identified in Islamic State videos and, in one recruitment footage, Khan proclaimed the group was planning "fireworks".

However, al-Arefe has previously denied supporting the Islamic State and condemned their brutality.

"My position vis-a-is Isis is very clear, I am vehemently opposed to the brutal methods employed by many of their fighters and condemn categorically their extremism," he said.

Qatar is also believed to be the primary financier of Hamas, the Islamist group battling Israel from the Gaza Strip. Former Israeli President Shimon Peres has said that the country is "the world's largest funder of terror".

"Qatar does not have the right to send money for rockets and tunnels which are fired at innocent civilians," Peres recently told UN Secretary-General Ban Ki-moon in Jerusalem.

"Their funding of terror must stop. If they want to build then they should, but they must not be allowed to destroy."

The Gulf State only holds a population of approximately 1.9 million but is one of the richest countries in the world due to its vast resources of oil and gas.