On Thursday, Gaza courts ordered partial recounts of 5 May local elections in two locations where Hamas swept to victory - the town of Bait Lahiya and the Buraij refugee camp.
Hamas branded the decision as politically motivated in the guise of a judicial decree. Thousands of Hamas supporters in both places later marched through the streets in protest, calling on the courts to let the original results stand.
Smaller numbers of Fatah backers were out celebrating, but there were no confrontations between the sides.
Earlier, a court ordered a partial re-vote in Rafah in the local election, seen as a harbinger for parliamentary balloting set for the summer.
Hamas called for reforming the courts that investigate contested election results, saying the courts were populated by Fatah members.
Committed to ceasefire
Meanwhile, Hamas announced it remains committed to a de facto ceasefire with Israel despite an eruption of violence in the Gaza Strip over the past two days, said a leader of the movement on Thursday.
"Hamas is still committed to calm and the issue is linked to Israeli attacks. If they are repeated, we will respond and if they stop, we will stop," Mahmud al-Zahar said, a day after a Hamas man was killed in an Israeli missile strike on a cell firing mortar bombs.
A second Hamas member was killed in disputed circumstances.