Italy said Thursday it would increase its military presence in the central Mediterranean, describing a deadly attack on a museum in Tunis as fresh evidence of a growing threat from extremist groups.

"Following a worsening of the terrorist threat, dramatically demonstrated by yesterday's events in Tunisia, an increase in our air and naval deployments in the central Mediterranean has become necessary," Defence Minister Roberta Pinotti told the parliamentary defence and foreign affairs committee.

At least two Italian tourists died in Wednesday's attack on the Bardo museum in Tunis.

The minister said the increased military presence was required to defend Italy's multiple interests in the area in light of the growing risk posed by the presence of extremist groups and to ensure consistent levels of maritime security.

"North Africa has to represent our primary concern," Pinotti told lawmakers.

On top of the forces usually deployed, Italy has moved additional naval units, a maritime protection team, helicopters, planes and drones into the area, she added.

Pinotti said the extra resources were needed to protect communication lines, merchant shipping and offshore platforms and to facilitate increased surveillance of potential jihadist activity.

Italy has been on a heightened state of alert on its own territory for the last month following Islamic State's execution of 21 Egyptian Christians in Libya and threats by the group that it could seek to carry out terror attacks on the former colonial power.

Italian security chiefs are concerned that IS appears to be gaining a foothold in conflict-wracked Libya and could use it as a base to mount attacks on merchant ships or on Italy.

The chaos in Libya is also seen as a key factor driving an acceleration in the number of migrants arriving on Italy's shores by boat with current rates pointing to more than 200,000 landing this year.

Italian Foreign Minister Paolo Gentiloni warned last month that IS loyalists could team up with battle-hardened militia fighters in Libya and seize control of parts of the country.

Rome says it is ready to lead a peacekeeping operation in Libya on condition that the warring parties agree to lay down their weapons and the UN issues a green light.