Mark Regev, the Israeli foreign ministry spokesman, said the arrests were "due to the fact that Hamas over the last few weeks has escalated terror attacks against Israel".
Jacob Dalal, an army spokesman, said: "They are not being used as bargaining chips. These are people with terrorist records, with allegations and charges pending against them."
An army spokeswoman said the ministers would be investigated, brought before a judge, their detention extended and charge sheets prepared.
During raids in Ram Allah and Jerusalem early on Thursday, at least eight Hamas cabinet ministers were detained.
Israeli troops detained five of the ministers at the same Ram Allah hotel, Aljazeera reported.
Some were led away blindfolded and in handcuffs, Palestinian security sources said.
Palestinian officials said Umar Abd al-Raziq, the Palestinian finance minister, and at least seven other cabinet members, along with nearly 20 Hamas legislators in operations across the West Bank were detained.
Israel said 64 Hamas officials in all were taken into custody during the West Bank operation.
"When the Israelis come, maybe we'll be stuck in our homes for God knows how long"
Isra Abu Anza
In a sign of worsening relations between Israelis and Palestinians, a planned summit between Ehud Olmert, the Israeli prime minister, and Mahmud Abbas, the Palestinian president, has been cancelled.
Abbas condemned the arrests of the Hamas politicians and called on Western powers to intervene to "restore democracy".
The Popular Resistance Committees (PRC) group, which claimed responsibility for the kidnapping of Corporal Gilad Shalit during a raid on an Israeli army post, said: "Olmert and [defence minister] Amir Peretz will be entirely responsible for the life of the kidnapped soldier if the aggression continues."
Palestinians lined up at public water fountains to fill up jugs after a second night of power cuts, under Israeli military pressure that has sparked fears of a humanitarian crisis in Gaza.
"When the Israelis come, maybe we'll be stuck in our homes for God knows how long," says Isra Abu Anza, a 16-year-old girl standing in a queue at one of the fountains.
Israeli aircraft bombed the Gaza
town of Khan Yunis
"We need to drink, to wash, to bathe."
An Israeli missile destroyed a crucial power station late on Tuesday. In Rafah, which relied on the destroyed power plant for half of its daily energy needs, residents are now left without power for much of the day.
The Israeli military continued to prepare for a ground assault on parts of Gaza.
In preparation for the offensive, Israel dropped leaflets on northern Gaza urging residents to avoid areas troops may single out for attack.
Israeli aircraft fired missiles at the southern Gaza Strip on Thursday, with the military saying it aimed at open areas, and Palestinian medical officials saying a car was hit.