Berlin police said on Sunday that four teenage men had been arrested for a violent attack on election campaign helpers for the Social Democrats (SDP) in the city the previous day. 

The youths are accused of subsequently insulting, assaulting and injuring police who tried to intervene. 

SPD politicians including party general secretary Matthias Miersch condemned the attack. 

"Such acts of violence show once again how dangerous right-wing extremism is for our society," he said. 

What police said about the incident

Police described the attack as appearing to be "motivated by right-wing extremism," saying the suspects had traveled from a different state to take part in a small far-right march through Berlin on Saturday. 

"The four suspects, who are thought to be part of the far-right scene, arrived around midday, in order to engage in physical altercations with 'leftists,'" police said in a statement. 

They encountered the SPD election campaign workers by chance at a bus stop in Lankwitz in the Lichterfelde district. One of them demonstratively threw the two people's hats to the ground and verbally insulted them before physically attacking, police said. 

"Both of them soon fell to the ground. The attackers are suspected of continuing to strike at one of them in the head and torso multiple times wearing heavy-duty jump boots," police said. 

When two nearby police officers tried to intervene, the youths racially insulted one of them before wounding them in the face with a shard of glass. The other officer sustained a fractured hand. 

The situation could only be defused once reinforcements arrived.

The two injured officers and one civilian all required hospital treatment but could be discharged after treatment. 

Police said the four men were being charged with two cases of collective grievous bodily harm, one of them of particular severity against law enforcement.

Counterdemos dwarfed Saturday's far-right march 

A local chapter of the SPD first raised the alarm about the attack on Instagram over the weekend, saying that a member had been thrown to the ground and kicked in the face and stomach. 

"Sadly we experience such crimes more and more often of late," the Berlin SPD state chairs Nicola Böcker-Giannini and Martin Hikel said in a joint statement. "This must be a warning for all democrats." 

One of the members attacked, Carolyn Macmillan, said afterwards that democrats must "stand together now, for we cannot give up our place in East Lichterfelde to the Nazis." 

Saturday's march through parts of Berlin went ahead relatively peacefully, although left-leaning counter demonstrators vastly outnumbered the main demonstration and forced it to alter its planned route more than once with a police escort. 

Police issued a follow-up report on Sunday saying 63 people took part in the main demonstration while more than 2,000 turned out to object at various counter protests.

Political campaigning and other activity is beginning to ramp up around the country ahead of the early parliamentary elections in February.

msh/sri (AFP, dpa, epd)