Hundreds of Democratic Front for the Liberation of Palestine supporters clashed with Israeli forces on Saturday and expressed support Palestinians held in Israel prisons.
An AFP correspondent said some 300 Palestinians threw stones at soldiers and blocked streets in Hawwara, south of Nablus, at the end of a rally marking the DFLP's 44th anniversary.
Demonstrators held pictures of Samer Issawi, a DFLP member, who is held in an Israeli prison and has been on an intermittent hunger strike since August.
A military spokeswoman said some 200 Palestinians had been throwing stones at soldiers, who responded with riot-dispersal methods.
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She added that two Palestinians had been detained at the site, but the army had not yet decided whether to arrest them.
Meanwhile, a delegation of European lawmakers paid a visit to Issawi's home in the Arab east Jerusalem neighbourhood of Issawiya. Six of them are in the region in a show of support for Palestinian detainees and prisoners in Israeli prisons.
Issawi was a long-term security prisoners released by Israel under a prisoner swap deal in October 2011, then re-arrested last year following allegations he violated the terms of the agreement.
Israel has ordered that he serve out the remainder of his original sentence.
The European delegation was protesting last week's sudden death of imprisoned militant Arafat Jaradat in an Israeli cell, which prompted Palestinian allegations of torture and several days of violent protest in the occupied West Bank.