London, Jun 21 (IANS): A Libyan youth held for allegedly stabbing three people to death in a terror incident in the UK's Reading town on Saturday evening was already on the radar of British security agencies, reports said on Sunday.

Police indicated that it seemed to be a solo attack.

Citing security sources, the BBC reported that Khairi Saadallah, 25, who was arrested at the scene on Saturday had came to the attention of MI5 last year after a tip-off that he had plans to travel to Syria - potentially for terrorism.

This was further investigated, but no genuine threat or immediate risk was identified, the BBC reported, adding no case was initiated, which would have made him a target for further investigation.

One victim was identified as teacher James Furlong - described by his school as "talented and inspirational".

Prime Minister Boris Johnson said he was "appalled and sickened" by the attack in Forbury Gardens on Saturday evening, and promised action following the incident "if there are lessons that we need to learn".

Metropolitan Police Assistant Commissioner Neil Basu, head of counter-terrorism policing, described it as an "atrocity" and said his "deepest sympathies go to the families who will be mourning loved ones after this horrific act".

Basu said investigators are not looking for anyone else in connection with the attack.

According to the Thames Valley Police, police were called to Forbury Gardens in Reading, about 80 km west of London, at about 7 p.m. on Saturday and "a number of people were injured and taken to hospital".

"Tragically, three of these people died, and another three sustained serious injuries," it said.

South Central Ambulance Service said early Sunday morning on Twitter that "we were assessing and treating a number of casualties who had sustained injuries as a result of the incident".

Several police patrol vehicles and two air ambulances arrived at the park after the attack, and the area was cordoned off.

According to witness reports in British media, the suspect apparently randomly stabbed people sitting the park and when he realized that people were running, the individual tried to flee the area.

The stabbings took place around three hours after a peaceful anti-racism protest by the Black Lives Matter movement had taken place.