Authorities in Italy have tightened security amid fears of further bomb attacks a day after explosions at two embassies in the capital wounded two people.

Police were on alert for new attacks at the weekend, following separate blasts at the Chilean and Swiss missions in Rome on Thursday.

An Italian anarchist group known as the Informal Anarchist Federation claimed responsibility for the mail bombs, saying the explosions were set off to avenge Chilean and Swiss anti-anarchist actions.

Al Jazeera's Sabina Castelfranco, reporting from Rome, said police presence was visible in the streets on Friday to ensure citizens feel safe, particularly ahead of Christmas.

"Concerns over security have been mounting here and came to a head with Thursday's explosions.

"Authorities in Rome are taking no more chances this Christmas," she said, adding that security was tightened ahead of Pope Benedict XVI's Christmas Day message on Saturday in the Vatican.

'Wave of terrorism'

All mail addressed to embassies in Rome was being carefully scrutinised after the explosions.

The blast at the Chilean embassy came just hours after the explosion in the mail room of the Swiss mission on Thursday. The two people injured in the attacks were wounded while opening the packages.

A third suspect package was found at the Ukrainian embassy, but did not appear to contain explosive materials, Yevhen Mitskevich, an embassy spokesman, said.

Gianni Alemanno, Rome's mayor, referred to the blasts as a "wave of terrorism against embassies" and said this was "much more worrisome than a single attack".

The blasts come after a rudimentary device was discovered in an empty underground train in Rome on Tuesday.

However, police said that the device lacked a detonator and tests showed it contained no explosive.