Israeli forces arrested three Hamas-affiliates in Nablus early Tuesday, locals said Maan reported.
Local Hamas leader and Imam in Asira al-Qibliya, Dirar Ahmad Mohammad Hamadneh, 53, was detained in an arrest raid, witnesses told Ma'an.
Zaher Sidqi Mousa and Shadad Shaher Abu Amsha, said to be Hamas members, were detained in west Nablus and taken to an unknown location after Israeli forces raided their homes.
An Israeli army spokeswoman said 12 people were arrested overnight for "illegal activity", without providing further details.
Four were detained in Nablus, five in Ramallah and three in Hebron, she said.
The latest arrests come as Israel launched a sweep of detentions against Hamas-affiliated officials in the West Bank overnight Sunday, including three Palestinian MPs.
Hamas said in a statement that the three Hamas lawmakers -- Ahmed Attoun in al-Bireh, Hatem Qafisha in Hebron and Mohammed al-Tal in al-Dhahiriyya -- had been detained in the early hours of the morning, labeling the detentions a "criminal act."
Twelve other Hamas officials were seized in the raids overnight Sunday, as well as several Palestinians not holding a political position, according to local sources.
An Israeli military spokeswoman said 25 Palestinians were arrested, with 23 belonging to the Islamist group.
PLO official Hanan Ashrawi said the arrests were an Israeli intrusion into internal Palestinian politics.
"It is apparent the Israeli government is implementing a policy of intimidation and power politics to meddle in Palestinian domestic affairs and to undermine reconciliation efforts," she said in a statement.
Israel holds 4,743 Palestinians in its prisons, including 178 held without charge, according to latest figures from prisoners group Addameer.
The Palestinian Authority says 15 MPs are currently detained in Israel jails.