The activists marched to the Square of the Unknown Soldier, and chanted "The people want to end the division," in reference to the bitter split between Gaza`s Hamas rulers and the Fatah-dominated Palestinian Authority in the West Bank.
"We are starting our sit-in now," organiser Ahmad Arar told AFP.
Banners and placards were everywhere, some reading: "Abbas, Haniya -- we want national unity!" in a direct address to president Mahmud Abbas and Hamas premier Ismail Haniya.
Others read: "We won`t go home until the end of the division."
Many brought tents and mattresses, while others were setting up water stations, with the intention of remaining in the square overnight until the official start of the demonstration on Tuesday.
The March 15 demonstrations are scheduled to take place simultaneously in Ramallah and Gaza City in a campaign put together on Facebook by a loose coalition of young activists who say they have no political affiliation.
Similar protests are also planned outside Palestinian delegations overseas, in a move inspired by the recent wave of uprisings in the Arab world which brought down the regimes of Egypt and Tunisia and inspired the revolt in Libya.
As more and more people arrived at the sit-in, there was a party-like atmosphere in the square, with youngsters waving flags, singing national songs and chanting slogans.
Huge loudspeakers blasted tunes from a popular Lebanese singer as young people stood around chatting or put up tents, some lounging on mattresses.
There were few signs of the security forces, although a handful of police could be seen directing traffic around the square, an AFP correspondent said.
Some activists said the decision to start the mass protests a day early was taken for fear the Hamas-run security forces would close off the square or block roads in a bid to prevent the planned rallies.
But Samah al-Rawah, another of the March 15 organisers, said the decision to start early came after the Hamas interior ministry refused to give them a permit to protest on March 15, saying another group had already applied to hold a protest that day.
Organisers believe the permit was handed to a Hamas organisation which is trying to co-opt the March 15 movement, which goes by the name The National Campaign for an End to Division.
"So we have started now because we don`t want any other Palestinian faction to steal this event. We will sleep here because we don`t want anyone else to take over the square," Rawah said.
Earlier on Monday, Haniya had ordered the interior ministry to let the rallies go ahead without interruption, his office said in a statement.
The premier, it said, "supports all the efforts by the young people and the factions which aims to end the division and protecting the... national unity of our people."
Haniya ordered the ministry to ensure the security forces "created an atmosphere which would let these public events succeed."
Later, a statement from the Hamas security forces said they would "work hard to protect these noble goals and will continue to keep the compass national and the public away from hateful partisanship that some people are trying to make up to poison the atmosphere."
Since the outbreak of massive protests in Egypt, Hamas security forces have clamped down on numerous demonstrations. Last week, they detained 11 "unity" protesters and interrogated those believed to be behind the Facebook campaign. (M014/K004)
Editor: Kunto Wibisono
Copyright © ANTARA 2011
