Supporters of Alexei Navalny, Russia’s imprisoned opposition leader, said that he has been suffering from unexplained stomach pain and had lost an alarming amount of weight, leading them to speculate that he is being gradually poisoned.

An ambulance had been called Friday to the high-security penal colony where Navalny is serving time after his condition took a turn for the worse due to a mystery stomach illness, lawyer Vadim Kobzev and spokesperson Kira Yarmysh said Tuesday.

Navalny, 46, was said to have shed 18 pounds over the course of 15 days while being held in solitary confinement.

Kobzev claimed that his client has not been receiving any treatment for his condition and that prison officials have been “brazenly” turning away packages containing medications, which Navalny’s mother has been sending him.

“In response to his question, ‘What ails me?’ the prison doctor replies to him: ‘Well, it’s springtime, and everyone has flare-ups,” Kobzev tweeted.

Judging by the “bizarre” situation surrounding Navalny’s health, “we are not ruling out that he is simply being slowly poisoned, so that his health would deteriorate not drastically, but rather gradually yet steadily,” Kobzev stated.

The attorney added that while the poisoning claim may sound like “ravings and paranoia in relation to someone else, but not to Navalny after ‘Novichok.’”

Kobzev was referring to the anti-Kremlin activist’s near-fatal poisoning with the “Novichok” nerve agent in Aug. 2020.

Navalny posted on social media Tuesday said he had been moved back into solitary confinement for the 13th time and forced to endure “extremely hellish” conditions.

Vladimir Putin’s vocal critic is serving combined sentences of more than 11 years on fraud and contempt of court charges, which he said were trumped up to silence him.

Navalny said he had been released from solitary confinement Friday and then sentenced to another 15 days in the “punishment cell” Monday, after his supporters on the outside released an investigation showing that the prison service was allegedly overpaying for cabbage and pocketing the surplus.

“That is why the very next day after my colleagues released their investigation about these fun cabbage stories, they put me in the [solitary confinement cell],” he wrote.

Navalny also said that he has been prohibited from buying food, even with the money he had earned, was being forced to take his daily walks at 7 a.m., and has had his letter-writing privileges sharply curtailed.

Additionally, Navalny’s lawyer claimed that a prison staffer has tipped off the opposition leader about a “provocation” involving another inmate that is purportedly being planned against him.

Last week, Russia said Navalny supporters had helped assassinate pro-war blogger Vladlen Tatarsky in St. Petersburg.