A spokeswoman for Russian opposition politician Aleksei Navalny, who is serving a 30-day jail term, says he has been hospitalized after suffering a "severe allergic reaction."
Kira Yarmysh said Navalny was taken from the Moscow detention facility to a hospital on the morning of July 28.
The opposition figure and Kremlin foe arrived at the hospital with “severe facial swelling and red rashes on the skin,” Yarmysh tweeted.
The source of the allergic reaction has not been determined yet, she wrote, adding that Navalny “never experienced an allergic reaction before.”
"He is currently in the ward under the supervision of police officers," she said in a separate tweet. "He is being provided with the necessary medical assistance."
Officials gave no details of Navalny's condition.
He was sentenced last week to 30 days for calling for an unsanctioned protest in Moscow on July 27, during which more than 1,300 people were detained by police, according to an independent group that monitors crackdowns on demonstrations.
Leonid Volkov, a top aide to Navalny, tweeted that he had a similar reaction after he served a sentence in the same cell as Navalny last month.
Volkov rejected talk of a "conspiracy" and called instead for a "serious inspection" of hygiene standards at the detention center.
Navalny had been sentenced to jail about a dozen times in recent years and has served more than 200 days in incarceration.