Published today (updated) 15/05/2011 19:32 GAZA CITY (Ma'an) --

An unidentified 18-year-old was killed and 125 others injured by Israeli fire during a march of Palestinians in Gaza toward the separation fence and Erez border with Israel on Sunday.

The group, estimated to number almost 1,000, marched in commemoration of the Palestinian expulsion from homes and villages in 1948 that accompanied the declaration of the state of Israel. The march began in the northern Gaza town of Beit Hanoun toward the Israeli border.

A medic told AFP that several hundred people had bypassed a Hamas checkpoint just south of the border, and came within a few hundred meters of a concrete border barrier installed by Israel near the Erez checkpoint when shots were fired.

Medical officials also said there were 40 injured by what was described as "poison gas," which officials said was dispersed in canisters toward protesters. They said the gas was not the usual tear-gas deployed by the military, and was causing serious respiratory difficulties.

Protesters calling for the right of return to their homes in what is now Israel, identified an Israeli patrol car, and began throwing stones and condemning Israel's continued siege on the coastal enclave, which is populated by mostly refugees.

Teenagers began throwing stones at an Israeli tank, which opened fire towards them.

An Israeli military statement said "Soldiers fired in a controlled manner in the direction, and towards the legs of the leading rioters, in order to disperse them and prevent them from entering Israeli territory. A number of rioters were injured as a result."

Medics told Ma'an that at least 82 demonstrators were injured by artillery shells and gunfire. The injured were mostly children, and some were critically injured, medical officials said. One journalist was also injured. They were taken by ambulances to hospitals in the northern Gaza Strip.

The day, known as Yom An-Nakba in Arabic, commemorates the "Day of Catastrophe," when the state of Israel was created, turning an estimated 800,000 Palestinians into refugees.

Most of the people who fled to the Gaza Strip in 1948 were from the city of Jaffa, south of what is now Tel Aviv, and the towns and villages between Jaffa and Gaza City, as well as from areas in Beersheba and the Negev.

Estimates from the UN's refugee agency said some 200,000 refugees fled to the Gaza Strip. The refugee population now numbers 1.1 million there, three quarters of the population.

AFP contributed to this report