In a statement Friday, Arbour said "the rising number of lives lost, whether as a result of targeted killings or suicide attacks, homemade missiles or artillery fire, is unacceptable."
The U.N. official said civilians, particularly women, children and the elderly, "should not pay the price for the neglect of human rights and humanitarian obligations."
Arbour said the Palestinian population is at risk as a result of cuts in international aid to the Palestinian Authority.
The United States and other Western nations have cut off direct aid to the Hamas-led Palestinian government over the militant group's refusal to renounce violence and recognize Israel.
In the latest violence, Israeli troops shot dead a Palestinian militant during a raid in the West Bank town of Nablus Friday. The Israeli army said the Palestinian was a member of the Al-Aqsa Martyrs Brigades militant group.
In another development Friday, an Israeli court charged four Palestinian militants in the 2001 assassination of Israeli Tourism Minister Rehavam Zeevi. The suspects are members of the radical Popular Front for the Liberation of Palestine, and were rounded up during an Israeli raid on a Palestinian prison in Jericho in March. Israel launched the raid over concerns the Palestinian Authority was going to release the men.
Some information for this report was provided by AP and Reuters.