MOSCOW (Reuters) - Russia turned away a prominent French researcher at its border and sent her back to France two days before she was due to give a talk in Moscow comparing protest sentiment in Russia and France, she said on Thursday.

Protests are a sensitive issue in Russia where human rights workers accuse authorities of breaking up protests by force and using other heavy-handed tactics to keep a lid on anti-government rallies. Moscow denies using excessive force.

Carine Clement, an expert on social movements who lived in Russia for more than 20 years and has a Russian daughter, was due on Friday to give a talk about the “yellow vests” protesters that have rocked France, but was not allowed into Russia.

“I’m in France, I was immediately sent back,” Clement wrote on Facebook. “One thing is clear, the system has lost its head,” she said.

Russia’s Federal Security Service (FSB) told Clement she had been banned from the country for 10 years because she was deemed a security threat, she said in comments to Russia’s Kommersant newspaper.

The FSB did not immediately reply to a request for comment.

“It’s up to the Russian authorities to explain this decision, which falls within their competence,” the French foreign ministry said.

A series of demonstrations flared in Moscow in July over political freedoms in what became the biggest sustained protest movement in the capital in years, but has now faded. Several protesters have faced criminal prosecution for offences at the rallies.

President Vladimir Putin said in August that Moscow would not allow protests like France’s yellow vests movement to erupt in Russia.