(CNN) -- Hundreds of thousands of Palestinians gathered in Gaza in a show of support for Palestinian Authority President Mahmoud Abbas' Fatah Party on Friday, the 48th anniversary of the party's founding.
Palestine Liberation Organization leaders say Fatah was officially founded in 1965 which coincided with its first major attack against Israel.
It was an unusual scene in Gaza because it was the first mass rally showing open support for Fatah since 2007. That is the year Hamas seized control of Gaza from Fatah, which now controls only the West Bank.
The number of people who showed up surprised many. Some participants slept in the Gaza City square after gathering there overnight and the crowds eventually grew so large by daytime that at least seven of the major streets around the rally were filled with people.
High-level Fatah Party officials also showed up for the event after entering Gaza for the first time since being ousted by Hamas. Leaders of both parties described it as another step toward unity. Abbas sent a message via video from his headquarters in the West Bank town of Ramallah that was played on huge screens set up in Gaza.
"Gaza was the first Palestinian territory to get rid of the occupation and settlement, and we want the blockage to be lifted so that it can be free and be linked to the rest of the nation," Abbas said.
An SMS sent out from a Hamas representative referred to the rally as a "celebration of national unity and a success for both Hamas and Fatah."
According to the Gaza ambulance service, at least 30 people were injured after fighting broke out due to overcrowding as well as political rivalry among supporters of different political leaders.
In advance of the rally there also was bickering between Fatah and Hamas over whether Hamas would allow Fatah supporters to gather in a large space that was highly visible. In the end an agreement was worked out and the festivities progressed with some people holding Fatah flags and others waving pictures of Abbas and late Palestinian Authority leader Yasser Arafat.
The two parties have been bitter rivals for years, but the relationship between the two parties thawed after the recent fighting between Israel and Gaza that lasted eight days and left dozens dead.
After the conflict, Hamas was given approval to hold its first rally in the West Bank, and a few weeks later Hamas allowed Fatah to hold a rally in Gaza.
Hamas considered it a victory when Israel decided not to send in ground troops. Days later, Abbas' ability to get non-member-state status for the Palestinian territories at the United Nations was also considered a victory.
Since then there has been talk of reconciliation from leaders of both parties, but no concrete steps have surfaced yet.
Fatah leadership has had a great deal of support from the West and has been warned over the years not to join hands with militant Hamas, which several countries have deemed a terrorist organization.
CNN's Talal Abu-Rahma contributed to this report.