The organization said the military commanders responsible for ordering the aerial and artillery attacks could be prosecuted for war crimes.
In a statement, Human Rights Watch said it has knowledge of at least 30 attacks on permanent and makeshift hospitals in the combat area since December 2008. One of the deadliest took place May 2, HRW said, when artillery shells struck Mullaivaikal hospital in the government-declared "no-fire zone," killing 68 people and wounding 87.
"Hospitals are supposed to be sanctuaries from shelling, not targets," said Brad Adams, Asia director at Human Rights Watch. "While doctors and nurses struggle to save lives in overcrowded and underequipped facilities, Sri Lankan army attacks have hit one hospital after another."
Human Rights Watch has criticized both the Sri Lankan armed forces and the separatist Liberation Tigers of Tamil Eelam (LTTE) for breaking international law during fighting in recent months.