The UN high commissioner for human rights has urged Israel to refrain from using excessive force against Palestinians, as hundreds gathered near the Gaza-Israel border for a fifth round of weekly protests.
Zeid Ra'ad Al Hussein said Israeli troops have not heeded warnings by the UN and others, repeatedly using lethal force against unarmed protesters over the past month.
Since the weekly marches began, 35 Palestinians have been killed and more than 1,500 wounded by Israeli soldiers firing from across the border fence, according to Gaza health officials.
Among those killed were four minors, including a 14-year-old boy.
"The loss of life is deplorable, and the staggering number of injuries caused by live ammunition only confirms the sense that excessive force has been used against demonstrators - not once, not twice, but repeatedly," the commissioner said.
The marches have been organised by Gaza's Hamas rulers, but have also been driven by widespread despair in the coastal territory of two million people after more than a decade of closed borders.
Israel and Egypt imposed the blockade in 2007 in response to a violent takeover of Gaza by the Islamic militant Hamas, which had won Palestinian parliament elections a year earlier.
The blockade has gutted Gaza's economy, driving up unemployment and leaving two-thirds of young people without jobs.
Since late March, thousands have demonstrated every Friday in five protest tent camps, several hundred metres from the border fence. Smaller groups have moved towards the fence, throwing stones, burning tyres and hurling firebombs.
Israeli soldiers including snipers have fired tear gas, rubber-coated steel pellets and live rounds.
On Friday, a significantly lower number of protesters turned out than in previous demonstrations.
In one area, east of Gaza City, several dozen people approached the border fence, some throwing stones. Israeli forces fired several rounds of tear gas.
Israel's military has said troops are under orders to target "instigators", but has also warned that anyone approaching or trying to damage the fence risks his life.
Israel has accused Hamas of using the protests as cover for attacks on the border, including planting explosives near the fence.
Israel says it has the right to defend its border, including nearby communities.
Rights groups have said such open-fire rules are unlawful because they allow soldiers to use potentially lethal force in situations where their lives are not in danger.
Mr Al Hussein said on Friday that "it is difficult to see" how throwing stones, burning tyres or even hurling firebombs from a distance at heavily protected security forces in defensive positions could be seen as life-threatening.
Gaza organisers say that in addition to compelling an end to the blockade, the marches are meant to press for the "right of return" of refugees and their descendants to what is now Israel. Two-thirds of Gaza residents are descendants of refugees.
Hundreds of thousands of Palestinians fled or were driven from their homes in the 1948 war over Israel's creation, and march organisers see May 15, the anniversary of Israel's founding, as a key target day.
They have made conflicting statements about whether they plan a mass border breach at some point.