STOCKHOLM, April 7 (Xinhua) -- Swedish Security Service SAPO said it would not raise threat level in wake of the suspected terror attack, Swedish Television reported Friday.
"It is continuously reviewed. For a long time it has been on a three on a five-point scale, and the threat level remains at a third. Within the level of fit that an attack may be happening, "SVT quoted SAPO press secretary Karl Melin as saying.
"We regard this as a special case and we are working closely with the police to act quickly. It's about the intelligence to find out who or what is behind, " said Melin.
Earlier on Friday night, Swedish police have arrested a man in the north of Stockholm in an operation, according to the Swedish paper Aftonbladet.
The man, arrested in Marsta, had minor injuries and said that he is guilty of the attack in Stockholm, Aftonbladet reported.
The death toll of Stockholm attack has risen to four, as one victim died in hospital. Swedish Television quoted hospital sources at Karolinska Institutet as saying that the number of injured people from the attack earlier had reached 15.