The coordinator of the organisations, Ahmad al-Kurd, also said on Sunday that five premature babies born in the past few days died because of a lack of available medical treatment.
"Out of the 1,000 or so victims of the blockade, 450 died as a result of the collapse of the health situation in Gaza, such as the lack of medical supplies and the crisis of medical referrals for outside treatment."
Gazans continue to face a desperate situation because of the blockade with water and electricity shortages, as well as a lack of medicines and doctors unable to perform surgeries.
Kurd said the use of alternative electricity by residents of the Gaza Strip since 2006 has caused the deaths of 100 people.
"The use of candles, firewood or generators has resulted in house fires that claimed the lives of children and adults alike," he said.
Furthermore, the number of workers who were killed in the fields of agriculture, fishing and commercial tunnels has reached 350.
Source: Al Jazeera