The video posted to Twitter lasts only 15 seconds. It shows a police officer restraining a young man by placing his knee on the suspect's neck, while people at the scene shout at the officer, demanding that he stop.

This footage of a police operation was recorded last weekend in the western German city of Düsseldorf, and has been compared to the scene that led to the death of George Floyd in Minneapolis in late May.

The 15-year-old suspect in the German video was reportedly unharmed, but the clip has nevertheless sparked a debate about the limits of police authority.

Incidents in Frankfurt, Hannover and Hamburg

The video from Düsseldorf showing an alleged disproportionate response by police isn't the only one to go viral on social media in recent days. In Frankfurt, an officer was filmed kicking a man on the ground who had refused to be detained. In a press statement, police spoke of an "improper use of force" and confirmed disciplinary measures against the official.

Similar videos have popped up showing scenes in the northern cities of Hannover and Hamburg. In the latter, a video showed a young man shouting that he couldn't breathe, as a group of officers stopped him. In a press release, the local police department said "deployment techniques were controlled so that the teenager was able to breathe at all times." 

These cases come after recent riots in the cities of Stuttgart and Frankfurt in June revealed tensions between youth and police, and after thousands of Germans joined the worldwide Black Lives Matter protests in reaction to George Floyd's death.

Read more: In Germany and France, cities shocked as youths riot and attack police

Police must be held to 'very high standards'

The incidents have prompted political reactions at a local level, but also from federal lawmakers in Berlin.

Mathias Middelberg is a member of Chancellor Angela Merkel's conservative Christian Democrats, and the domestic policy spokesman for the conservative parliamentary group. When asked by DW to comment on these incidents, he said that "of course" they must be taken seriously. He added, however, that "the police must not be judged hastily."

"The first priority now is a full investigation of the operations by the judiciary," he said.

Irene Mihalic, a police officer by training and a member of parliament for the opposition Green party, told DW that "use of force can be necessary if the situation requires it, but only then."

But, she added, "police of a democratic constitutional state like ours must rightly measure their actions by very high standards."

Commenting on the Düsseldorf video, Mihalic told DW that the footage "shows the use of a method that endangers the health and life of the detained person for reasons I cannot see." She said the situation must now be clarified in detail.

Read more: Racial profiling leads to debate over Germany's policing methods

Police in the spotlight

Police action has been in the spotlight in Germany in recent years, although not to the extent of the United States.

Herbert Reul, the conservative interior minister of the state of North Rhine-Westphalia, of which Düsseldorf is the capital, explained that physical violence by police is not illegal per se, but in some cases "appropriate, permissible and absolutely necessary."

But police operations can also lead to an important number of cases of excessive force on the part of officers, as revealed in a recent study by the Ruhr University Bochum.

The study found more than 3,300 cases in which victims had reported excessive physical violence by police. However, researchers also stressed that many cases charges or criminal proceedings weren't initiated, meaning a large number of cases remained in the dark. 

"While this does not necessarily mean that this is true for society as a whole, the findings allow us to deduce that the overall dark figure concerning unlawful police use of force is presumably at least five times as large as the official figures," said the report. The researchers also found that the criminal proceedings that had been initiated showed "a remarkably high number of dismissed cases, and a very low number of indictments."

In the most recent cases in Düsseldorf, Frankfurt and Hamburg, investigations to determine whether police actions were justified are still in the early stages.

Read more: Police in Germany under the pall of right-wing extremists

Uli Grötsch, a member of parliament for the center-left Social Democrats, said details of these police operations should preferably be probed by an independent body.

"The vast majority of citizens have confidence in the police," he told DW. "For this to remain so and even to be expanded, we must clarify each individual case meticulously and consistently."

"The police themselves have an interest in this," he said.