In a brief visit, during which she also met Palestinian president Mahmud Abbas, Louise Arbour listened to local residents talk about this month's Israeli offensive against Beit Hanun where some 80 people were killed.
"The violations of human rights in the Palestinian territories are intolerable," she told reporters, explaining that her visit was to express UN condolences and show concern for civilians.
"I think it's clear that civilians are tremendously exposed," said Arbour, wearing a dove broach.
She was speaking not far from the Nasser mosque, one of the oldest mosques in Gaza whose lone minaret is all that remains after the offensive before heading into talks with Abbas at his Gaza City seafront office.
"This is a very moving experience and it has brought home to me the exposure and vulnerability of civilians in Gaza in particular," she told reporters following the talks with the Palestinian leader.
She emphasised that she would stress to both Israeli and Palestinian authorities the need to protect civilians, just hours after Gaza militants fired another eight Palestinian rockets towards the Jewish state.
More than 60 Palestinians, around half of them militants, were killed during a six-day operation in Beit Hanun to halt rocket attacks on Israel, and 19 others, mostly women and children, died in an Israeli shelling on November 8.
"We are very happy to see you here, to see our suffering. We hope to see more visits like your visit to see how we are suffering from the IDF (army) invasions," Kamal Kafarneh, who lost relatives in the shelling, told Arbour.
At the house most heavily damaged by the shelling, the commissioner listened to two middle-aged women from Karfarneh's wider family tell their stories, patting them gently on the shoulder to comfort them as they wept.
Relative Majdi Kafarneh told the commissioner and journalists what happened that day, saying that 32 members of his extended family were wounded in the raid and were now being treated in hospitals in Egypt, Gaza, Israel and Jordan.
Israel charged that militants hijacked Beit Hanun as a launchpad for rocket attacks aimed at its territory, thereby provoking the six-day operation.
Israel has said a technical error was responsible for the artillery shelling on November 8 and expressed regret for the "tragedy".
Arbour's visit comes less than a week after the UN Human Rights Council voted last Wednesday to send an urgent fact-finding mission to Beit Hanun to examine the impact of Israel's attack on the Palestinian homes.
Thirty-two countries, mainly from Asia, Africa and the Middle East, voted for the resolution introduced by Arab and Islamic nations at the 47 member Council, which was subsequently denounced by Washington as "imbalanced".
Israel has also lashed out at a UN General Assembly resolution calling for a probe into the botched shelling.
More than 300 Palestinians have died in Gaza since Israel launched its deadly military offensive there in late June.

Copyright AFP (Agence France-Presse), 2006