Rioters looted shops in central Frankfurt late Saturday night following protests in German cities over rising inflation and living difficulties.
Along with the economic capital of Germany, incidents of violence also took place in Berlin, Cologne and Hamburg.
Police say protesters fired fireworks, threw stones and bottles at emergency services workers, after which water cannons were used to disperse the crowd.
Earlier in the day, thousands of people had participated in largely peaceful demonstrations. These demonstrations were organized by a campaign group called 'Gen Ze Regalt', which means 'Gen Ze takes charge'.
The protesters were protesting against inadequate funding in schools, rising cost of living, cuts in government spending and military service.
This unrest in Germany follows similar major youth-led demonstrations in France. More than 3 lakh 20 thousand people demonstrated here on Saturday.
By night these demonstrations turned violent.
Police closed off a large section of Frankfurt's main shopping street. A police spokesperson said that several people have been arrested in the city.
Officials in Frankfurt, Munich and Berlin said there were a total of about 18,000 protesters in these cities, which was about half the estimate given on the organizers' website.
According to German media, thousands of people demonstrated in many cities of Germany on Saturday.
Gen Z Regelt spokeswoman Lena Friedrich said the demonstrations were aimed at "fighting for peace and freedom instead of war and coercion."
He said, "The most important thing for us is to better support the health and education systems. We are against compulsory military service and want the burden placed on the people to be distributed in a more fair way."
On Saturday night, Frankfurt police said "violent rioting" was taking place in the city center and special police forces had been deployed.
According to police, windows of several shops were broken and Molotov cocktails were thrown at emergency services workers.
Officials said the windows of an arms shop were also broken. After arresting a suspect, two weapons were recovered from him.
According to local media, people also entered other shops and stole shoes and other items.
Interior Minister Roman Posek of Frankfurt, the largest city in the state of Hesse, said "about 100 clearly identified left-wing extremists" had joined the demonstration in the city.
He said the way these demonstrations ended was "shameful".
Posek said, "We all have those images of France in our minds, including looting, burning of houses, burning of police vehicles and attacks on police officers. France should not be presented as a model in this matter."
Police said that the situation in the city became calm by early Sunday morning.
Similar incidents happened in other cities of Germany also. Before this, most of the demonstrations in these cities were peaceful.
Police in Cologne said that policemen were attacked near the main railway station. Bottles were thrown at them and a bicycle was also hurled at them.
Cologne police chief Johannes Hermans said, "It is extremely sad that among the youth who wanted to demonstrate peacefully for their future, such extremists, whose only aim was to cause violence, intruded."
After big demonstrations during the day, a small demonstration took place in Berlin in the evening. According to Berlin Police, 27 policemen were injured during this period and 56 people were detained for some time.
In Hamburg, people dressed in black set off fireworks and set fire to barricades. According to public broadcaster NDR, 120 people were arrested during this period.
These demonstrations took place in Germany on the same day when large-scale protests were taking place in other countries of Europe.
In France, for the third consecutive weekend, massive demonstrations took place in different cities of the country. More than three lakh 20 thousand people took part in these. Most of the demonstrations remained peaceful.
The protesters were demanding improvements in the rising cost of living and the poor state of public services, especially the education system.
Thousands of police were deployed across France to deal with the demonstrations. In some cities, police fired tear gas shells at protesters.
More than 500 people were arrested after clashes in Toulouse, Lyon and Marseille.
French Interior Minister Laurent Nunez said a police officer was injured by a Molotov cocktail. According to Paris police, several hundred rioters attacked police forces by throwing objects.
There were demonstrations in Italy also. There were some clashes between police and protesters in Rome and Turin.
Police in Portugal took action to remove a new temporary camp made of tents. This camp was formed after a march of thousands of people who demonstrated against a bill related to rent.
Protestors say that this bill may further increase the housing crisis in the country.
House prices in Portugal have more than doubled in the last decade.
In recent days, in many countries of Europe, most of the youth are taking to the streets and protesting. These include France, Belgium, Ireland, Spain, Portugal, Italy, Greece, Serbia and Albania.
