A medical trade union leader and ally of Kremlin critic Alexei Navalny said on Thursday she and her group were asking the jailed opposition politician to call off his hunger strike. "To continue (the strike) would be dangerous for his life and health," Anastasia Vasilyeva, head of the Doctors Alliance union, told Reuters. "We very much hope Alexei will end the hunger strike tomorrow." Russia"s leading opposition politician began a hunger strike on March 31 to demand proper medical care for leg and back pain that he said he was being denied to him in prison. Having survived a nerve agent poisoning last year that Russia denies carrying out, Navalny is serving a 2-1/2 year sentence in a case that he and his supporters say is politically motivated. Russia says he has been treated well and is exaggerating to gain attention. President Vladimir Putin makes a point of never speaking Navalny"s name, and the Kremlin says the case is a matter for the prison service. Police detained more than 1,900 Russians on Wednesday as his supporters took to the streets in dozens of cities to show backing for the 44-year-old opposition politician, according to the OVD-Info protest monitoring group. Vasilyeva also said that authorities had taken Navalny to a civilian hospital on Tuesday, a day before the protest, and that he had been seen by the head kidney specialist, neurologist and neurosurgeon there. Navalny"s team had not until now said he had been seen by doctors outside of the prison where he is being held in Vladimir region, east of Moscow. Leonid Volkov, a close Navalny ally who is outside the country, said they had received the results of his medical checkup on Thursday, something he cast as a victory for their protest action. Vasilyeva called into question the course of medical treatment that was prescribed for him and said the team of doctors would publish their full medical report on Friday.