More than 1000 people confirmed attendance to the protest's morning portion-- spanning from 5 a.m. to around noon--within their digital RSVP form, according to event media contact Wassim Hage.
Organizers expect a few thousand protesters to join their occupation of the port in the afternoon. They began planning the event late last week, according to Hage.
The port opened at 9 a.m.
The protesters say that aid has contributed to a humanitarian crisis in Gaza.
United Nations officials have described scenes of "utter horror" on the streets there.
VIDEO: Hundreds of pro-Palestinian protesters march in downtown SF, calling for end to Israel-Hamas war
Hundreds of pro-Palestinian protesters march in downtown SF
A CNN investigation found at least 20 out of the 22 hospitals in northern Gaza were damaged or destroyed in the first two months of the war - with 14 being directly hit.
The Hamas-run health ministry says nearly 24,000 Palestinians have been killed by Israeli attacks since October 7.
The group Save the Children says some 10,000 of the dead are children.
The conflict is also spreading.
MORE: Demonstrators call for Israel-Hamas cease-fire outside Nancy Pelosi's SF home
On Saturday, the U.S. carried out more strikes against Houthi rebels in Yemen.
They are attacking shipping lanes in the Red Sea in support of Palestinians.
Bay City News contributed to this report
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