Alexei Navalny's doctor was detained outside his prison after asking to check on him, as reports say the Russian critic is seriously ill

• Russian police detained the doctor of opposition leader Alexei Navalny at a protest over his health.
• She was turned away from the prison after saying she wanted to check on him, Reuters reported.
• Navalny was transferred to a medical unit because of possible respiratory problems and fever, Reuters reported.

Russian police detained Russian opposition figure Alexei Navalny's doctor after she asked to check on his health.

Reuters reported that Anastasiya Vasilyeva, who is an ally of Navalny and leads a doctors' union, was detained after she was turned away from the prison, where she said she had an appointment with a senior prison official and that she wanted to see Navalny to check on his health.

Al Jazeera described Vasilyeva as Navalny's personal doctor.

At least six other people were detained, including two CNN correspondents, at the protest, Reuters reported.

It is not clear why they were detained.

Navalny was transferred to a penal-colony medical unit earlier this week because of possible respiratory problems and fever, Reuters reported on Monday. His lawyer has said he was "seriously ill."

Navalny recently announced a hunger strike to process a lack of medical care in the facility.

He was sentenced to 2 1/2 years in prison in early February for violating a 2014 suspended sentence. He missed probation meetings because he was being treated for poison in Berlin, his lawyers said.