"The teachers say that when they hear a loud noise they (the children) look to the sky and cry out and weep. They don't know what the future holds," she told the joint media conference with Egyptian actor Mahmoud Kabil, also a UNICEF ambassador.
"They deserve better," she said.
She later spoke out for the children of Sderot, an Israeli city just a few kilometres (miles) from the Gaza border that is regularly targeted by rockets fired by Palestinian militants.
She said she spoke with children who prayed they would "never again hear the sound of rockets, not wake up with that fear. Surely that is the right of every child," she said.
"Please God may there be peace," she told journalists outside the Sderot police station where she viewed a pile of mainly homemade rockets that slammed into the city and surrounding areas.
Farrow, 64, travelled to Gaza on Wednesday and met children working in smuggling tunnels along the Egypt border, toured a school and a hospital and was briefed on the impact on children of the Gaza war as well as the blockade.
Israel and Egypt have kept the aid-dependent territory of 1.5 million people, more than half of them under 18, sealed to all but essential humanitarian goods since the Islamist Hamas violently seized power in June 2007.
Israel launched a December-January war on the territory in response to persistent rocket fire. The offensive killed some 1,400 Palestinians and 13 Israelis and left large swathes of Gaza in ruins.
Farrow was to make several visits in Israel and the occupied West Bank before leaving for Jordan on Sunday at the end of her week-long visit.
Once a fashion model, Farrow has appeared in more than 40 films, including 13 in which she co-starred with Woody Allen, with whom she had a 12-year relationship.
A high-profile advocate for children's rights and the mother of 14 -- 10 of them adopted -- Farrow has worked to draw attention to polio, which she survived as a child, and has visited conflict zones in Africa, including Sudan's Darfur region.
Time magazine put her on its list of the world's most influential people last year.
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