As the Qatar crisis continues, following Qatar's rejection of the Saudi-led demands to end the boycott of the small Gulf state, accusations of terror funding remain central in the debate. Germany's foreign minister says his country's intelligence service will participate in efforts to clear up accusations by Arab neighbors that Qatar supports terror groups, while a study was recently published in the U.K. claiming Saudi Arabia is the biggest funder of terror in the country, which has been reeling from a wave of deadly attacks.

Foreign Minister Sigmar Gabriel visited Saudi Arabia, Qatar and mediator Kuwait this week as the Saudis and others seek to isolate Qatar over its alleged support for extremists.

Gabriel told Deutschlandfunk radio Thursday there was an agreement for Qatar to "open all its books" to Germany's intelligence service "if we have questions about certain people or structures."

The minister said he no longer sees the risk of a military escalation in the standoff despite an angry reaction Wednesday from the four Arab nations to Qatar's response to their demands. Gabriel said that, while the reaction sounded harsh, many demands were no longer mentioned.

Germany's vow to help Qatar clear its name came a day after Saudi Arabia was accused of being the biggest promoter of Islamist extremism in Britain, funding mosques, religious training and publications, claimed a new study published on Wednesday.

Saudi Arabia has "sponsored a multimillion-dollar effort to export Wahhabi Islam across the Islamic world, including to Muslim communities in the West," said the study by the Henry Jackson Society, a think tank focussing on human rights and international relations.

It said Saudi Arabia operates several large charities that fund Islamic education worldwide, including in Britain, spending at least 67 billion pounds (87 billion dollars) on the programmes over the past 50 years.

"However, in practice, the form of education advanced by these institutions involves a concerted effort to promote the hardline Wahhabi interpretation of Islam endorsed by the Saudi state," it said, highlighting the role of the World Assembly of Muslim Youth (WAMY) and the Muslim World League (MWL).

The influence of the Saudi funding is seen in Britain and other Western nations through the "prevalence of Islamist extremist preachers and literature, including the use of Saudi school textbooks," and scholarships for clerics to train in Saudi Arabia.

The promotion of Salafi-Wahhabi ideology has "gradually contributed to changing the climate of religious belief and practice" in many Muslim communities, the study found, and "created a challenge for moderate voices and empowered extremists."

The release of the study comes amid pressure on Prime Minister Theresa May to publish an apparently delayed government report examining the role of Saudi Arabia and other nations in encouraging extremism in Britain.

The Associated Press contributed to this report