Newly-selected Italian Interior Minister Marco Minniti was working with police chief Franco Gabrielli on Tuesday morning to co-ordinate a response to the attack.
Minniti also convened an urgent meeting with Italy's anti-terrorism committee (CASA) to evaluate the country's threat level, at which it was decided to "strengthen checks" at areas visited by large numbers of people.
As in many European countries, Italy's big cities are home to busy Christmas markets, particularly in the northern region on South Tyrol.
In Bolzano, where one of the most popular markets is held, police commissioner Lucio Carluccio said: "The already well-functioning security unit has been alerted and additional teams deployed."
The security measures already in place at the northern Italian market include a team made up of volunteer doctors and security experts, all of whom underwent three months' training and are equipped with bullet proof vests and an armoured car.
Milan's Christmas market closed for half an hour at 3pm on Tuesday to pay tribute to the victims of the attack, one of whom is thought to be a young Italian woman.
Anti-truck barriers were also introduced in the city, after the region's prefect called an emergency meeting to discuss the security situation.
Authorities also introduced additional "traffic management techniques" to keep larger vehicles away from groups of tourists, and an increase in police units deployed in "the most sensitive areas" which included Milan's canals, shopping centres and markets.
Security in Rome, Turin and Florence was also beefed up on Tuesday.
Italy's security alert level has been at 2, the highest possible in the absence of a direct attack, since the Paris attacks in November last year.
The country and in particular the capital, Rome, has been the target of persistent threats from Isis and other terror groups.
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