THESSALONIKI — An anarchist group on Monday claimed responsibility for last week’s attempted bomb attack against a senior judge in Greece, raising fears of a resurgence of violence by radical militants.

Explosives experts defused the parcel bomb that was placed at a courthouse in the northern city of Thessaloniki and addressed to the judge.

In an online post, a previously unheard of group, called Armed Response, claimed responsibility for the attempted attack. It named the judge it had targeted and vowed to step up attacks against the judiciary in solidarity with jailed fellow militants.

“Just as easily as the parcel bomb reached her office, our bullets can find their target,” the statement said.

Greece has a decades-old history of attacks by anarchist and far-left militant groups, ranging from small arson attacks, to bombings and assassinations. Relatively few attacks have occurred in recent years, but several have taken place over the past few weeks.

Earlier this month, a bomb exploded in central Athens outside the labor ministry, causing no injuries. It followed a warning call by a group calling itself Revolutionary Class Self-Defense.

In December, a bomb that failed to detonate was placed outside a police facility in Athens.