German minister Gerd Mueller has accused Qatar of financing the Islamic State in Iraq and Syria (Isis), the extremist group that seized control of large swathes of Iraq in July and has been responsible for dozens of atrocities including mass executions and crucifixions.

“A story like this always has a history,” he said speaking in an interview with German broadcaster ZDF. “Who is financing these troops? Hint: Qatar.”

Isis declared an Islamic caliphate that straddles both Iraq and Syria on 4 July and is implementing a strict interpretation of sharia law in cities it controls in both countries.

The accusation from the German development aid minister comes five months after former Iraqi Prime Minister Nouri al-Maliki accused both Saudi Arabia and Qatar of funding the Sunni Muslim insurgents that were battling his troops in Anbar province.

Speaking on France 24 he said, “I accuse them of inciting and encouraging the terrorist movements. I accuse them of supporting them politically and in the media, of supporting them with money and by buying weapons for them”.

Both Saudi Arabia and Qatar rejected Iraq’s accusations, though US think tanks have said they believe money is flowing to Isis from individuals in the two countries.

On Friday 15 August the UN Security Council passed a resolution blacklisting six individuals for helping to recruit fighters and finance jihadists in Iraq and Syria.

Two of those blacklisted were from Saudi Arabia, two were from Kuwait, one was Algerian and another was Iraqi. None of those blacklisted were from Qatar.

Over recent weeks the US has launched air strikes on Isis positions in Iraq.

Last week the European Union gave member states permission to supply arms to Iraqi’s Kurds to help them battle Isis militants. Germany is due to decide on whether it will send arms later this week.