Cross-border gunfire killed an Egyptian policeman and wounded five Palestinians after youths hurled rocks over the border fence during a protest in southern Gaza, officials said.
The 21-year-old officer succumbed to his wounds in hospital in the divided border town of Rafah, an Egyptian security official said.
Witnesses in Gaza said shots were fired from both sides of the border and medics said five Palestinians suffered serious gunshot wounds.
Witnesses said the Egyptians opened fire after about 200 young Palestinians hurled stones at them.
An Egyptian security official said nine policemen were slightly wounded by the stone-throwing.
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Fifteen Palestinians were wounded when Hamas security officials used batons and teargas and fired shots in the air, to disperse the stone-throwers.
The incidents took place following a demonstration called by the Hamas rulers of Gaza to protest Egypt's construction of an underground barrier meant to stop smuggling through cross-border tunnels.
Egypt deployed hundreds of officers to reinforce the border as well as fire trucks and ambulances amid concerns Palestinians might try to breach the border during the protest. Hamas called the incident "regrettable."
"We are not interested in raising tension at the border," said Sami Abu Zuhri, a spokesman for Hamas.
But he said the protest was the result of the anger felt in Gaza over the Egyptian decision to build the underground barrier.
Hundreds of demonstrators held up green Hamas flags and chanted "God is greatest."
"One metre away from Egypt, we ask: 'why the siege?'" Hamas MP Mushir al-Masri told the demonstrators.
"We came today to say no to the wall," he said.
Israel and Egypt have imposed a blockade on the impoverished territory since Hamas seized control of the coastal strip in 2007 after ousting forces loyal to Western-backed Palestinian president Mahmud Abbas.
Hundreds of tunnels have since been used to smuggle consumer goods and weapons into the territory.
Masri said the protest also aimed at demonstrating solidarity with pro-Palestinian activists who clashed with Egyptian police at the nearby El-Arish port on Tuesday.
About 55 people were injured in the clashes.
Tuesday's clashes started after some 520 activists accompanying an aid convoy for Gaza broke down a gate at the port to protest Egypt's decision to allow only 139 of the convoy's 198 vehicles to enter the Gaza Strip through the Rafah crossing.
