The initiative was started in cooperation with the International Committee of the Red Cross and the Palestinian Red Crescent Society.
"We are launching a blood donation campaign that responds to the call of the Lebanese minister of health," said Alaa al-Batta, mayor of Khan Younis, according to The New Arab.
Batta explained that Palestinians in Gaza are ready to stand in solidarity with the victims in Lebanon.
Abdul Qader Idris, a 45-year-old, told Xinhua news that he donated blood to "repay" Lebanon for its strong ties with the Palestinian people and for protecting "the Palestinian resistance over the past years."
Rescuers sifted rubble in a race to find anyone still alive after Tuesday's port explosion that killed 154 people, injured 5,000, destroyed a swathe of the Mediterranean city and sent seismic shockwaves around the region.
Hospitals in the capital were overwhelmed with the injured and began treating people in hallways and transferring other wounded people to locations outside of Beirut. Fatalities, injuries and damage were reported on streets and in buildings throughout Beirut. Lebanese citizens were asked to donate blood if possible and doctors were asked to come immediately and help treat the wounded.
Reuters contributed to this report.