Four Palestinians were killed Wednesday in an explosion in the Gaza Strip, the Health Ministry said.
A ministry statement said 19 other people were injured, including some seriously, in the explosion that occurred in eastern Gaza near a security fence along border with Israel.
The cause of the explosion was not yet clear.
The incident occurred as hundreds of Palestinians gathered near the security fence to mark the anniversary of Israel's pullout from the seaside territory in 2005.
Israeli forces fired rubber-coated bullets and tear gas canisters to disperse the crowd, according to witnesses.
Israel pulled out its forces from the Gaza Strip on Sept. 22, 2005 as part of a disengagement plan by then-Prime Minister Ariel Sharon.
Home to nearly 2.3 million Palestinians, Gaza has been reeling under a years-long Israeli blockade since 2007, badly affecting livelihood in the enclave.
