A reinforced fence and more than 100 bollards will also be installed at Flinders Street Station and Princes Bridge to protect against hostile car and terrorist attacks, the Minister for Police and Emergency Services Lisa Neville said on Friday.

Making the announcement, Ms Neville also revealed that design plans for upgrades involving Southern Cross were already underway.

The works are the next stage of the $50 million security upgrades planned for six busy Melbourne sites in 2019. The other four sites include Southbank, the Olympic and Melbourne park area, the State Library and Queen Victoria Market.

The security upgrades, incited by the 2017 deadly Bourke Street attack, are expected to replace the concrete bollards currently at some of the sites.

“It’s all about making our city of Melbourne, our state of Victoria, more resilient, more able to withstand risk of terrorism,” said Ms Neville.

Under the plans, 20 bollards will be installed around Flinders Street Station. An eight metre long concrete barrier, which will have railings up to a meter tall above it, will run along the Flinders Street on the side of the station.

There are also plans for 88 more reinforced concrete blocks, which will be placed along both sides of Princes Bridge, replacing the current water-filled barriers.

The plans also involve a 130 square metre expansion of the Flinders Street Station forecourt.

“It has taken quite a significant amount of time to get the security and engineering design right,” Ms Neville said of the Flinders Street station upgrades.

“Each and every one of these of these sites is very unique, both in terms of the risk as well as the particular areas around the concrete underlay.”

Installation of the upgrades will start on Monday January 14 and will take between four and six weeks.

Pedestrians crossing Princes Bridge should expect some disturbances, though one side of the footpath will always be open.