Mass protests in Gaza on Tuesday were violently broken up by Hamas police officers and security officers, many in plainclothes, witnesses said.

The demonstrations, organized by independent Palestinian youth activists, called for national unity.

At least five people, including three local journalists, were treated at a hospital after being beaten at the demonstration, employees at the hospital said.

The day’s events both exposed Palestinian divisions and underscored the popular desire for political reconciliation between Gaza, controlled by Hamas, and the West Bank, controlled by the Palestinian Authority under Mahmoud Abbas amd his Fatah party.

During the day, thousands of demonstrators who gathered at Al Katiba Square, carrying only Palestinian flags, clashed with supporters of Hamas, an Islamic militant group, who tried to force their way into the square.

The demonstrations, ignited by youths through social networking sites, were the biggest independent rallies since Hamas took full control of Gaza in 2007. They were inspired by the popular movements that brought down authoritarian governments in Tunisia and Egypt.

The split deepened in 2007 when Hamas, which won parliamentary elections a year earlier, routed the pro-Abbas forces in Gaza.

The rally Tuesday began as planned in Gaza’s Square of the Unknown Soldier, and for a moment in the early morning it appeared to be emerging as the symbolicheart of a new unity movement.

But before long the Hamas supporters arrived and pushed their way into the square. Frustrated at the sight of Hamas flags and slogans, the protest organizers and hundreds of their supporters left the square and marched in the streets nearby.

They returned to the square, then went again into the streets before finally settling in Al Katiba, where they were joined by thousands more demonstrators.

Since Al Katiba was not the planned destination, men and women, mostly young, stood in the sandy field in the sun with no water, seats or loud speakers. But all shouted passionately against the division between Hamas and Fatah.

A man dressed in the military uniform and keffiya of the late Palestinian leader Yasir Arafat was carried on the shoulders of others in front of unarmed Hamas policemen as people chanted, “The people and the police are one hand!”

A scuffle broke out between the protesters and dozens of Hamas supporters, who refused to lower their Hamas flags as they tried to enter Al Katiba.

The protests seemed to elicit a quick response from the Palestinian leadership. On Tuesday, officials in Gaza and the West Bank, where smaller gatherings took place, found rare common ground, professing their desire for reconciliation.

Ismail Haniya, who leads the Hamas government in Gaza, invited Mr. Abbas and Fatah to resume national unity talks at any time or place.

Officials of the Fatah-dominated Palestinian Authority attended a demonstration of several thousand people in Ramallah, and the authority issued a statement saying it welcomed the popular movement to end the schism.

Mr. Abbas proposed holding presidential and parliamentary elections as soon as possible as a way of ending the split — an idea that so far has been rejected by Hamas.

Naji Shurrab, a political science professor at Al Azhar University in Gaza, which is unofficially affiliated with Fatah, said on Tuesday that ending the Fatah-Hamas split was beyond the capacity of the youths to correct. “The division is like cancer; the later you are in treating it, the more it spreads,” he said.

Mr. Shurrab also criticized Hamas for demanding things unrelated to the split as conditions for a reconciliation, such as repudiating the Oslo agreements with Israel and ending security cooperation betweenthe Palestinian Authority and Israel.

The Gaza Interior Ministry hoped that the protesters would end their activities at 5 p.m. But more tents were erected at Al Katiba in the evening, until they were evacuated by force.

The organizers said they would march again on Wednesday.