Akilov was apprehended by police at 7.55pm on Friday, then officially arrested at 1.15am the following morning.
A pre-trial hearing is to be held tomorrow at 10am.
“When it comes to the state of the investigation I feel very confident that we have the right perpetrator who drove the truck,” national police chief Dan Eliasson said at a press conference earlier in the day.
“We have several different forms of evidence. We have forensic evidence, we have images, and information from the individual himself,” he added. “After that, it's up to the prosecutor to prove it in court.”
Eliasson also reiterated that the 39-year-old had shown an interest in extremism, including extremist organizations like Isis, but that nothing suggested he would carry out a terror attack.
READ ALSO: Sweden remembers truck attack victims
Stockholm District Court has rejected a request from Akilov to change his public defence counsel.
A request has not yet been lodged to remand the second suspect who has been arrested in relation to the attack. The prosecutor has until 12pm on Wednesday to make a request.
In an update on their website, Stockholm Police explained that there are links between the two suspects, but they cannot go into detail over what that entails or how it emerged.
Police are currently working to map out the two men by checking their history of contact with other people, their telephone conversations, digital communications and financial transactions.
The police have several ongoing operations related to the investigation and expect to take more people in for questioning. They said that it is not possible to say how many are currently in police custody because people are constantly being questioned then let go if they can be ruled out from the investigation, but revealed that a number of homes had been searched on Monday.