British police said on Sunday they had arrested a second man in connection with an attack in London two days earlier, in which a terrorist suspect assaulted officers with a 1.5-meter (4-foot) sword.

"The man was arrested on suspicion of being involved in the commission, preparation or instigation of terrorism at 10:15 a.m. (0915 UTC) today and he has been taken into custody," they said in a statement.

Police had earlier stated their belief that the attacker was acting alone.

British counterterrorism police launched their investigation after a man was arrested on Friday for the sword attack on officers outside Buckingham Palace. He had previously driven a car at police outside the palace, which is often used as a residence by Queen Elizabeth II and her family.

Queen not in residence

The man was quickly subdued with pepper spray by the unarmed police. But he injured three officers, two of whom were hospitalized with light injuries, as was the attacker, who reportedly shouted "Allahu akbar" (Arabic for "God is Greatest") several times during the struggle.

The 26-year-old man from Luton, 50 km (30 miles) northwest of the capital, has been taken to a London police station for questioning.

Neither the queen nor any members of the royal family were in Buckingham Palace at the time of the attack.

Last October, a man convicted of murder climbed a palace wall and was detained on the grounds while the queen was at home.

Europe on alert 

The attack occurred just an hour after a machete-wielding terror suspect attacked soldiers in Belgium. He was shot dead.

The incidents come as the United Kingdom and much of Europe are on high alert following a series of deadly attacks over the past two years. Jihadis have claimed responsibility for most of the attacks.

In Britain alone, nearly three dozen people have been killed in three separate attacks in London and Manchester since March.

Two of those involved a vehicle plowing into pedestrians.

The other attack, in May, was a bombing at a pop concert by US star Ariana Grande in Manchester, which killed 22 people, including children.

Read more: Madrid to Manchester to Barcelona: A chronology of terror in Europe

tj/jlw (AP, AFP, Reuters, dpa)