Brussels - A knife-wielding man was shot dead on Friday after wounding a soldier in the centre of Brussels, in what Belgian authorities called a "terrorist attack".The man, who prosecutors said yelled "Allahu akbar" (God is greatest) during the assault, was shot by soldiers on a street in the city which has been on high alert since terrorist attacks on its metro and airport last year."We believe that it is a terrorist attack," said a prosecutors' office spokeswoman, who added the attacker "is dead."Belgian media reported that the assailant was of Somali origin and about 30 years old.The same evening, in London two police officers were slightly injured arresting a man with a large knife outside Buckingham Palace but there were no immediate indications of a terror link.The incidents come after attacks claimed by the Islamic State group in Spain last week killed 15 people and a knifeman's stabbing spree in Finland left two dead and eight wounded.One of the two soldiers targeted in Brussels was "slightly" wounded, according to federal prosecutors, who have opened a terror probe of the attack."All our support for our military," tweeted Belgian Prime Minister Charles Michel. "Our security services remain attentive, we are monitoring the situation closely with the Crisis Center," he added.City mayor Philippe Close told reporters the incident was the work of a "lone individual"."I heard yelling and straight away two shots," a witness named Yohan told AFP, who did not wish to give his surname.As he approached, he said he saw "a soldier bleeding from his hand and a man on the ground," who had a beard and was wearing a hood.The attack took place shortly after 8:00 pm (18:00 GMT) on a boulevard in the centre of Brussels, near the Grand Place central square, one of the "sensitive" areas of the capital where armed soldiers patrol because of the terrorist threat in Belgium.Troops on streetsSoldiers have been deployed at railway stations and landmark buildings in Brussels since the Paris terror attacks in 2015, when a link to the Belgian capital was first established. Their presence has been reinforced since suicide bombers struck Zavantem Airport and the Maalbeek metro station near the EU quarter of Brussels in March 2016, killing 32 people and wounding hundreds more.The Islamic State group claimed responsibility for the attacks, which were carried out by the same Brussels-based cell behind the November 2015 suicide bombings and shootings in Paris which left 130 dead.In June a man who tried to bomb a Brussels train station was shot dead by a soldier.Belgian authorities identified the man in that incident as a 36-year-old Moroccan national with the initials O.Z., while local media named him as Oussama Zariouh.No one was injured in the foiled attack at Brussels Central station but officials said the consequences could have been severe had the bomb, full of nails and gas canisters, detonated properly.The man shouted "Allahu Akbar" during the attack and prosecutors said he had sympathies for IS.Police found explosive materials in a June raid on the home of the suspect in Molenbeek, a Brussels district which has been linked to recent deadly terror plots in France and Belgium.Belgian soldiers and police have repeatedly been the target of attacks in recent months.In August last year, an Algerian living in Belgium attacked two policemen in front of the police station in Charleroi shouting "Allah Akbar" and wounding them in the face and neck before he was killed. IS claimed responsibility for that attack.A month later, two policemen were stabbed in Molenbeek but without injury due to their bullet-proof vests.The attacker was of Maghrebian origin but without any clear link to the Islamist movement, according to the Brussels prosecutor's office.In October, two police officers were wounded by a knife-wielding man in Schaerbeek.