Police in Greece on Friday said they had arrested three people in connection to attacks this month that targeted ruling party politicians, killing a woman in a car explosion.
Hours later, two more people were held over a 2010 deadly firebomb attack that left three dead.
In the recent case, "three individuals have been arrested" by anti-terror police in Thessaloniki and the island of Crete, the police said in a statement.
The July 1 attacks at dawn in the northern city of Thessaloniki targeted the homes and vehicles of three politicians from Greece's ruling New Democracy party with homemade gas canister explosives.
The mother of former party candidate Afroditi Nestora died from injuries caused by an explosion, apparently while trying to put out the fire.
The attack also injured Nestora, her father and two other people.
Four vehicles in the garage of Nestora's home were burnt, police said.
Greek media identified the other two targets as the party's local executive committee chairman Zisis Ioakimovic and former MP Savvas Anastasiades.
Prime Minister Kyriakos Mitsotakis, the New Democracy leader, expressed "outrage and anger" at what he termed a "cowardly, terrorist and murderous attack".
Leftist and anarchist groups often use improvised explosives to target political figures, banks and companies in Greece -- causing damage but rarely any casualties.
The improvised explosives were made from small butane canisters, police said, and the attacks appear to have been carried out by the same people.
Greek media on Friday identified the detainees as young anti-establishment figures known to police.
Government spokesman Pavlos Marinakis has said that the attacks took place within 15 minutes.
Also Friday, police in Athens said they had arrested two people and were seeking a third over the 2010 bank attack.
On May 5, 2010 an anti-austerity protest saw a firebomb lobbed at the Marfin bank in central Athens, leading to the death of three bank workers, including a pregnant woman.
Three bank officials received manslaughter sentences for negligence but the culprits were never caught.
The attack came just three days after the socialist government of George Papandreou signed the first of three eventual bailouts with the European Commission, the European Central Bank and the IMF that would total 350 billion euros.
