Members of Hamas fanned out across the Gaza Strip on Tuesday, draping the Islamist resistance movement's flag across buildings ahead of a mass rally to celebrate their 23rd anniversary.

Tens of thousands of Palestinians were expected at the celebration being held in Gaza City's Kateeba Square, where an enormous replica of Jerusalem's Dome of the Rock mosque, with its famous golden dome, was being erected.

Large pictures of Hamas' leaders, including the group's assassinated spiritual guide Sheikh Ahmed Yassin, were displayed under a banner reading "I remain committed to the cause."

Hamas said it had sent buses to bring supporters to the rally from across the coastal enclave, and children at government-run schools and students at three Hamas-affiliated universities were given the day off for the event.

Members of some of Gaza's political factions, including Islamic Jihad, were expected to attend. Hamas's major rival Fatah, however, was likely to be noticeably absent. Hamas and Fatah remain bitterly divided after long-standing tensions boiled over in 2007, a year after Hamas won parliamentary elections, and Fatah, disregarding the results, held on to power causing a split within the Palestinian territories.

Hamas policeman clad in blue fatigues and bullet-proof vests closed streets leading to Kateeba Square as the interior ministry said it had finalised preparations.

The leadership of the group, including Hamas Prime Minister Ismail Haniya, was expected to address the rally, which is scheduled start at 1000 GMT.

Hamas spokesman Sami Abu Zuhri said the rally would provide evidence of the group's support in Gaza.

"The basic message the big crowds will send to all the parties is that lots of people support Hamas and the project of Hamas is the project of all the people," Abu Zuhri told AFP.

"The aim of the embargo on the Hamas movement and the Gaza Strip was to force us to raise the white flag of surrender, but Hamas will not break," he added.

Israel imposed a blockade on the Gaza Strip after the capture of a soldier by a Gaza-based resistance group in a deadly cross-border raid in 2006. It tightened the restrictions the next year after Hamas won a decisive majority in the Palestinian parliamentary elections.

Hamas was founded on 14 December 1987, shortly after the beginning of the first Intifada (uprising) against Israel's illegal occupation of the West Bank and Gaza Strip.