Germany’s interior minister has called for restraint after far-right politicians sought to exploit for political gain the death of an eight-year-old boy who was pushed in front of a train at Frankfurt station this week.

An Eritrean-born man who lives in Switzerland is accused of pushing the boy and his mother onto the tracks. The mother was able to roll to safety under the platform seconds before a high-speed train hit her son, killing him instantly.

Local media reported that the boy and his mother were on their way to Austria for their summer holiday at the time of the attack. The suspect fled but was intercepted by passengers, including an off-duty police officer, who tackled him to the ground. He faces charges of murder and attempted murder.

“The country is polarised,” Horst Seehofer, the German interior minister, said on Wednesday, and even though actual crime levels were down, “the feeling of security in the population is very strained right now”. Strict measures must be taken against criminals, he added, but “we cannot allow either the exploitation nor the downplaying of crimes by immigrants”.

Politicians from the far-right party Alternative für Deutschland (AfD) were quick to emphasise the fact that the suspect, identified by police as Habte Araya, was an Eritrean on the run from police in neighbouring Switzerland.

Shortly after the attack, AfD – alluding to the summer and autumn of 2015 when the chancellor, Angela Merkel, allowed an estimated 1 million refugees into the country – tweeted: “How many citizens have to be offered up on the altar of this welcome culture which knows no bounds?”

Alice Weidel, the party’s co-leader, said the attack was the latest evidence that the government’s open policy towards refugees in 2015 had put Germans in danger.

“The horror of this crime can hardly be beaten,” she tweeted. “What else needs to happen? Once and for all protect the citizens of this country instead of this boundless welcome culture!”

Konstantin von Notz, a Green MP, called Weidel’s tweet “appalling” and accused her of making political capital out of the Frankfurt killing. “To connect the harrowing crime in Frankfurt with the 2015 refugee crisis in order to profit from it, is glaringly false and politically simply the most extreme level of disgusting – though it’s clearly part of the AfD’s method,” he tweeted.

The Frankfurt killing is the latest in a series of high-profile crimes perpetrated by non-German citizens - including the gang rape of an 18-year-old-girl in the Ruhr valley town of Mülheim by Bulgarian youths and the death of a 34-year-old woman who was also pushed onto train tracks, for which a Kosovan man has been charged – which the AfD has seized on.

The party’s unrelenting criticism of Merkel’s so-called “open door” approach has helped fuel its elevation to the main opposition party in the Bundestag.

Tensions are also running high over a series of crimes attributed to the far right, including the racially motivated shooting of a 26-year-old Eritrean man in Wächtersbach, near Frankfurt, threats made against members of the far-left Die Linke party and attacks on mosques across the country. The most prominent incident in recent months was the murder of the pro-refugee Christian Democratic Union politician Walter Lübcke. According to prosecutors his suspected killer has numerous links to the far right.

Since Monday passersby have being laying flowers, cuddly toys, candles and chocolates on platform seven, where the boy died. A fierce debate over how to protect Germany’s rail passengers is dominating news networks, with many calling for a greater police presence and more closed-circuit television.

Hundreds of people gathered at the station on Tuesday night for an event organised by the railway’s religious mission to pay tribute to the boy and express support to his family.

Police separated about 50 far-right demonstrators from the rest of the crowd, including a woman who held a banner which read “This politics is killing the people”. A man aligned to a leftwing group shouted in her direction: “He should have pushed you in front of the train.”

People should not allow “hatred to spread”, said Carsten Baumann, the head of the railway mission, who called for unity.

“A glance at social media shows that this crime is being misused in order to divide society. But we cannot allow hate to seize us,” he said, adding that his thoughts were with the boy’s parents “who have lost everything that their son meant to them”.