German police have arrested a 28-year-old Syrian man in the northern port city of Hamburg on suspicion of planning an Islamist attack, police and prosecutors announced on Tuesday.

His brother, who is four years younger and lives in Kempten near the Austrian border in the southern state of Bavaria, is suspected of having aided and abetted in the planning of the alleged attack, according to the Federal Criminal Police Office, the Hamburg Criminal Police Office and the Hamburg Public Prosecutor’s Office.

A police officer has died and another was injured following a stabbing attack in Brussels, which a Belgian judicial official said was suspected to be terrorism-linked.

The suspected attacker was shot and “neutralised” after the stabbing and taken to hospital, Belgian police said.

“One of our patrols was attacked by a man armed with a knife,” police said.

“The two police officers then called for reinforcements. An officer from another patrol used his firearm to neutralise the attacker.”

Police added: “The two injured detectives and the assailant were taken to hospital.”

A judicial official who could not be quoted by name because the investigation is ongoing told The Associated Press there is “a suspicion of a terror attack”.

The official did not elaborate.

According to Belgian media, the attacker shouted “Allahu akbar”, the Arabic phrase for “God is great”.

Le Soir newspaper said the dead police officer was stabbed in the neck and died in hospital.

Belgian prime minister Alexander De Croo posted a message of condolence to the family and friends of the dead officer.

“Our police officers risk their lives every day to ensure the safety of our citizens,” he said.

“Today’s tragedy demonstrates this once again.”

Interior minister Annelies Verlinden said she was in contact with the Brussels mayor, police chief and security services to co-ordinate the response to the attack.

“Such violence against our people is unacceptable,” she said.

The attack took place at about 7.15pm local time.

Three men were “executed” in a Reading park by a “ruthlessly efficient” terrorist in less than one minute, a court has heard.

Khairi Saadallah, 26, shouted “Allahu akhbar” during the violent spree which left teacher James Furlong, 36, scientist David Wails, 49, and US citizen Joseph Ritchie-Bennett, 39, dead.

Three other people – Stephen Young, Patrick Edwards and Nishit Nisudan – were also injured before Saadallah threw away the knife and ran off, pursued by an off-duty police officer.

The failed Libyan asylum seeker had launched the attacks in Forbury Gardens, Reading, as the victims were enjoying a summer evening on June 20 last year after the first lockdown restrictions in England were relaxed.

Roger Smith, who was among the victims’ group, saw Mr Ritchie-Bennett “just going over sideways, like a tree being felled” as he was stabbed in the neck.

He said it “all happened really quickly” and was like a “weird dream”.

Another eyewitness, Andrew Cafe, said: “I saw him holding the knife and as he was charging towards us he shouted ‘Allah Akbar’.”

As Saadallah was detained, a Muslim member of the public told him: “You have nothing to do with Islam, bastard,” adding: “I am just livid.”

Following his arrest, Saadallah initially said he wanted to plead guilty to the “jihad that I done” but later feigned mental illness in police interviews.

Saadallah, of Basingstoke Road, Reading, pleaded guilty to three murders and three attempted murders and appeared at the Old Bailey on Tuesday for the start of his sentencing.

Prosecutor Alison Morgan QC said Saadallah aimed to kill as many people as possible in the name of violent jihad.

She said: “In just half a minute, the defendant was able to inflict catastrophic injuries to three people and serious injuries to three others.

“The prosecution’s case was that this was not an accident. This was not a frenzied attack by someone wielding a knife in a random, uncontrolled manner.

“The defendant was aiming to inflict the maximum amount of damage in the shortest possible time to allow him to kill as many people as possible.

“In effect, the killings of Joseph Ritchie-Bennett, David Wails and James Furlong were highly effective executions.”

Mr Ritchie-Bennett and Mr Furlong both suffered single stab wounds to the neck, and Mr Wails was stabbed once to the back.

Ms Morgan said the defendant was “ruthlessly efficient” in his actions, having planned and executed the attack with “determination and precision”.

The court heard that Saadallah, who arrived in Britain in 2012, had previously been involved with militias who had been part of the uprising against Muammar Gaddafi and was pictured handling weapons, including firearms.

Since living in Britain he had been repeatedly arrested and convicted of various offences, including theft and assault, between 2013 and last year.

He developed an emotionally unstable and anti-social personality disorder, with his behaviour worsened by alcohol and cannabis misuse, the court was told.

In 2017, the “impressionable and volatile” defendant associated at HMP Bullingdon with prominent radical preacher Omar Brooks, who is associated with the banned terrorist organisation Al-Muhajiroun.

An examination of his mobile phone revealed his interest in extremist material, including the flag of the so-called Islamic State and Jihadi John.

The court was told Saadallah was released from HMP Bullingdon on June 5, just days before the attack.

He then researched the location for his attack online and carried out reconnaissance on June 17, the court heard.

On June 18, he was in contact with his probation officer who alerted his mental health team over concern about comments Saadallah had made about “magic”.

Saadallah contacted the crisis team himself, but when they visited him on June 19, he did not open the door.

Police visited him the same day, prompted by concerns from his brother, but Saadallah insisted he was “alright”, while standing near a knife he had bought from Morrisons supermarket.

The court heard that a psychiatrist had since concluded that the events of June 20 were “unrelated to the effects of either mental disorder or substance misuse”.

Mr Justice Sweeney adjourned the hearing until Wednesday and said the sentencing would conclude on Monday.

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