A British paratrooper has been arrested in Austria for allegedly sexually abusing a six-year-old child, authorities said Thursday.

"An investigation has been launched against a British soldier on suspicion of aggravated sexual abuse of a child," Hansjoerg Mayr, public prosecutor in the western city of Innsbruck, told Agence France-Presse.

The Austrian government announced Monday the creation of a hotline and advice center for people to contact if they suspect a family member, classmate or colleague to be involved with Islamic extremists.

Austria, like other European countries, has seen a stream of young people, some in their teens, leave to join Islamic State (IS) militants in Syria and Iraq, sparking concerns that on returning they may launch attacks.

Austrian police arrested 13 people and raided homes, prayer rooms and mosques around the country early Friday in a mass operation targeting suspected jihad recruiters, prosecutors said.

The operation in Vienna and the cities of Graz and Linz was reportedly one of the biggest ever for the country, involving some 900 police officers.

A 14-year-old boy in Austria was remanded in custody Wednesday after telling police he planned to plant a bomb in a public area and join jihadists in Syria, authorities said.

The unnamed boy, a Turkish citizen living in Austria for at least the past eight years, had been under investigation since early October and was arrested on Tuesday, police said.

Iran's foreign minister said Tuesday "numerous questions" remain in talks with world powers aimed at breaking a deadlock in nuclear negotiations, as a delegation he led held fresh discussions with U.S. and EU representatives in Vienna.

The two sides have just six weeks before a November 24 deadline by which they are meant to come up with a final accord aimed at reducing fears Iran's nuclear program could be used to make atomic weapons, in exchange for lifting harsh Western economic sanctions.

Two people were seriously wounded Saturday as a Kurdish demonstration was attacked by radical Muslims in the western Austrian city of Bregenz, police said, days after clashes in neighboring Germany left 23 injured.

The two men were rushed to hospital with stab wounds in the stomach and one was in critical condition, a police spokesman said. 

U.S. Secretary of State John Kerry, Iranian Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton will hold nuclear talks in Vienna next week, Ashton's spokesman said Wednesday.

Ashton will first hold bilateral talks next Tuesday with Zarif, and "they will be joined by U.S. Secretary of State John Kerry for a trilateral meeting on Wednesday," spokesman Michael Mann said.

Austrian authorities said Tuesday they were investigating reports that one of two teenage girls who traveled to Syria earlier this year to join Islamist militants has been killed.

"Rumors are circulating on the Internet and we are checking that information," interior ministry spokesman Karl-Heinz Grundboeck told AFP, confirming local newspaper reports.

An Austrian court has lifted a freeze on the assets of the wife of a former U.S. ambassador to Afghanistan and Iraq, imposed during a money-laundering probe, officials said Friday.

Austrian police prevented two schoolgirls aged 14 and 15 from travelling to Syria, officials said Wednesday with press reports saying they wanted to join Islamist guerrillas.