Israeli forces arrested 20 members of the ruling Palestinian party Hamas, including three MPs, in dawn raids in the West Bank today.
Hamas said that MPs Ahmed Attoun, Hatem Qafisha and Mohammed al-Talhad had been arrested along with several local Hamas leaders.
"It is a criminal act that will not succeed in stopping their struggle," Hamas said.
"We in the Hamas movement strongly condemn the campaign of arbitrary arrests that took in dozens of Hamas leaders."
An Israeli military spokeswoman would say only that 25 Palestinians had been arrested and that 23 of them were Hamas members.
One of those arrested was the Hamas official in charge of reconciling with President Mahmoud Abbas's Fatah party.
Palestinians have been deeply divided since Hamas, which held a majority in Palestinian elections, took direct control of Gaza in 2007 after a bloody dispute with Fatah.
Mr Abbas has since ruled only in parts of the West Bank, and Hamas in Gaza.
So far attempts to reconcile the two groups have failed, but both sides have taken strides towards unity since a brutal Israeli attack on the Gaza Strip in November and Mr Abbas's succesful bid for UN-recognised statehood.