"The threat level has not been raised, but after what happened, we think Stockholm residents need to see more police around town, to talk to us about this very serious event that has taken place," Stockholm police spokesman Kjell Lindgren told AFP.
"We have an additional force of around 40 police officers, in addition to volunteers, who are out on the street, in the subways, train stations, shopping centres and everywhere it is crowded to make our presence felt," he added.
A spokesperson for Stockholm’s Arlanda airport on Tuesday refused to divulge what addition security measures, if any, had been put in place.
“Naturally, this event has been dealt with from a security perspective by Arlanda, but what measures we’re taking is obviously something we never comment on,” Arlanda’s Jan Lindqvist told the TT news agency.
“Our recommendation is to ‘come in plenty of time and pack correctly’, mostly due to the fact that significantly more people usually travel this time of year and there are heavy traffic days ahead of Christmas. But that we had that recommendation long before Saturday and it’s not related to those events in any way.”
Stockholm public transit operator SL, however, has deployed extra security guards following Saturday’s suicide bombing.
“We’ve got more security guards and guards, which will hopefully help people feel secure on the metro and in other places,” SL spokesperson Thomas Silvander told TT.
The transit agency has also told station attendants and guards to have increased vigilance and to report anything that appears out of the ordinary.
A man strongly believed to have been Taimour Abdulwahab was the only person to die Saturday when he first blew up his car and shortly after himself near a crowded pedestrian street in central Stockholm.
Two other people were injured by the car blast.
He was carrying a cocktail of explosives, and is believed to have mistakenly set off a small explosion that killed him before he could carry out what appears to have been a mission to kill "as many people as possible," Sweden's chief prosecutor for security cases, Tomas Lindstrand, said Monday.
Sweden's intelligence agency Säpo meanwhile said it had launched "a broad international cooperation" with authorities "in the other Nordic countries, the rest of Europe and of course in the United States" in their search for possible accomplices of the bomber.
"We are looking into different kinds of leads," Säpo spokeswoman Sofia Oliv told AFP Tuesday, without giving details.
Oliv refused to comment on work mapping Islamic extremists within Sweden, but according to the Aftonbladet daily, a yet unpublished report from the intelligence agency shows it knows of around 200 such people living in the Scandinavian country.
According to the paper, up to 80 percent of these people were part of so-called "violence-prone networks," while the remainder were "loners" and people with extremist contacts abroad.
Abdulwahab would have been 29 the day after the blasts.
He was reportedly born in Iraq, but investigators said he became a Swedish citizen 18 years ago. He had never come to the attention of the security services, they added.
An Islamist website, Shumukh al-Islam, posted a purported will by Abdulwahab which said he was fulfilling a threat by Al-Qaeda in Iraq to attack Sweden.
On Saturday, Säpo and the TT news agency received an email with audio files in which a man believed to be the bomber is heard calling on "all hidden mujahedeen in Europe, and especially in Sweden, it is now the time to fight back."