The watchdog accused Turkish border guards of shooting at some of those displaced in Aleppo province by fighting between the Islamic State (IS) group and rebels as they approached the frontier.
"As civilians flee ISIS fighters, Turkey is responding with live ammunition instead of compassion," said HRW researcher Gerry Simpson, using another acronym for the jihadists.
"The whole world is talking about fighting ISIS, and yet those most at risk of becoming victims of its horrific abuses are trapped on the wrong side of a concrete wall."
The UN Office for the Coordination of Humanitarian Affairs (OCHA) meanwhile estimated that up to around 23,000 displaced people had fled the IS offensive in northern Syria.
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It said many displaced were now "in close proximity to frontlines and therefore extremely vulnerable to further escalations".
It comes as escalating fighting between Russian-backed regime fighters and rebels around the provincial capital Aleppo further south threatens a nearly seven-week ceasefire that had seen violence drop significantly for the first time in the five-year conflict.
Representatives of Syrian President Bashar al-Assad's regime are expected in Geneva today for the latest round of talks aimed at ending the war, which has killed more than 270,000 people and displaced half the population.