Israel fired two tank shells and several rounds from machine guns as Gazans approached the heavily fortified border with Israel on Sunday, wounding at least 15 youths, a Palestinian health official said. One of the wounded was in critical condition.
The march near the Gaza-Israel border was part of Palestinian commemorations of their uprooting three generations ago during the war over Israel's establishment.
Across the West Bank and Gaza, thousands took to the streets, waving flags and holding old keys to symbolize their dreams of reclaiming property they lost when Israel was created on May 15, 1948.
In Gaza, dozens of marchers approached the border with Israel, and Israeli troops opened fire. The tank shells fell in an empty field several hundred yards (meters) from the group.
Palestinian health official Adham Abu Salmiya said 15 people were wounded by bullets and shrapnel. All of them were under 18 years old, and one was in critical condition, he said.
The Israeli military had no immediate comment.
Inside Israel, police were on high alert for disturbances among the country's Arab minority. In a reflection of the jitters, a deadly traffic accident involving an Arab truck driver in Tel Aviv set off fears that an attack had been carried out.
The truck plowed through a crowded street, crashing into a bus, several cars and pedestrians, killing one and injuring 16 others. Police said the 22-year-old driver claimed it was an accident, but said they were still investigating.