“Israel has committed an indefensible act,” the agency quoted Persson as saying, after Israel’s biggest military operation in a year continued overnight with helicopter gunships firing on the Gaza office of Hamas premier Ismail Haniya.
“It is disproportionate in terms of what the Palestinians have done,” Persson said.
“To go like that and remove part of a government and members of parliament is incompatible with international law.”
Israel has arrested 64 Hamas members including ministers and other officials since the soldier, 19-year-old Gilad Shalit, was kidnapped on June 25 during a Palestinian attack.
The Ezzedine al-Qassam Brigades, the armed branch of Hamas, has claimed responsibility for the kidnapping along with two other militant groups.
The groups have demanded that Israel free other prisoners it is holding, without explicitly saying whether this would entail a handover of Shalit in return.
Persson cast doubt on the possibility of an exchange of prisoners.
The situation “keeps getting worse and the dialogue between Israelis and Palestinians has now become virtually impossible. It is ominous,” he said.
The Hamas party took office in March but is dismissed as a terror group by Israel and the West.
A minister of the Hamas-led Palestinian government met with Swedish lawmakers in May, despite a European Union policy of no contact with the movement.