A two-year-old boy and a man aged 41 have been killed in a stabbing in a German park.

Police confirmed that a 28-year-old man from Afghanistan was arrested following the attack in Bavarian city of Aschaffenburg. German reports suggested he had a history of mental health issues.

Two others were taken to hospital with serious injuries and the public park was cordoned off by officers.

Markus Söder, the Bavarian state premier, called the attack a “cowardly and despicable act”. It is the latest fatal knife attack in Germany in recent months, and comes weeks before a federal election on 23 February.

Police said their investigation into the stabbing was ongoing, but that the attack had taken place at about 11:45 (10:45 GMT) at Schöntal Park in Aschaffenburg, about 22 miles (36 kilometres) south-east of Frankfurt.

The attack involved a kindergarten group according to the Spiegel website, which said other children were among those hurt.

Söder described the man killed as “a helper who paid for his civil courage with his own life”.

The suspect was arrested close to the scene after officers were called at around 11:45 local time (10:45 GMT). Officers said a second person was initially detained at the scene but was now being treated as a witness.

Police said there was no danger to the public.

Markus Söder said it was a terrible day and called for a pause: “We mourn the loss of a small, innocent child.”

Police said they were investigating a motive and the background to the attack remained unclear. The suspect was said to have been staying in accommodation for asylum seekers.

Chancellor Olaf Scholz, who was on a visit to France, condemned an “unbelievable act of terror”. He posted on social media that he was tired of seeing “such acts of violence every few weeks” and urged authorities to find out why the suspect was still in Germany.

The German government has come under increasing pressure to take a harder line on immigration after a number of fatal attacks, and with federal elections due on 23 February, the anti-immigration, far-right AfD is second in the polls.

Five people were killed when a man rammed his car into a crowd at Magdeburg’s Christmas market in December. A Saudi doctor has been charged with the attack.

In August, three people were fatally stabbed in the town of Solingen. The suspect was a Syrian national facing deportation after a failed asylum.

That attack led to the German government expanding border checks and tightening controls on knives, and fuelled an intense debate over asylum rules that has continued in the run up to next month’s election.

The conservative Christian Democratic Union (CDU) currently lead the polls and Olaf Scholz’s centre-left Social Democratic Party (SDP) are behind in third place.

The election was called after Scholz’s three-party coalition collapsed in November.