Russian police have arrested four people on suspicion of assaulting police officers at opposition protests this summer, the Investigative Committee said on Monday, an announcement likely to be condemned by the Kremlin’s critics.

The jailing of a handful of other protesters on charges including assaulting police at political rallies that began in July caused a public outcry.

Russians took to the streets when a slew of opposition politicians were barred from taking part in a local election in the capital, rallies that grew into the biggest sustained protest movement in the Russian capital in years.

The opposition accused the authorities of giving tough jail sentences to several protesters to scare others from joining the rallies. The conviction of one man for injuring a police officer was later overturned in court after it sparked public anger.

The quashing of that sentence last month was seen by some opposition activists as a way of de-escalating tensions with Kremlin critics while avoiding making bigger concessions.

On Monday, the Investigative Committee, the state body that investigates major crimes, said four more people had been taken into custody for breaking the law at a July 27 protest.

Two of the men pushed a police officer to the ground after which one of them kicked him, it said in a statement. In other incidents, one person shoved a police officer and another held a police officer back with force, it said.

Russian police are also looking for two other suspects who have gone into hiding, the Investigative Committee said.