Israeli fire killed six Palestinians and wounded scores during clashes Friday near Gaza's border, the first unrest-related deaths there after days of violence in the occupied east Jerusalem and the West Bank, medics said.

The clashes came as Hamas's chief in Gaza called violence that has hit the occupied West Bank and annexed east Jerusalem an intifada, or uprising, and urged further unrest.

Ahmed al-Hirbawi, Shadi Dawla, Abed al-Wahidi and Nabil Sharaf, all aged 20, were killed when soldiers responded after youths threw stones at them on the Israel side of their common border east of Khan Yunis, Gaza medics said.

Mohammed al-Raqab, 15, and Adnan Abu Alian, 20, were killed in similar clashes east of Gaza City.

Medics said another 80 Palestinians were wounded, 10 of them seriously.

An army spokeswoman said about 200 Palestinians had approached the fence while hurling rocks and rolling burning tyres toward security forces.

"Forces on the site responded with fire toward the main instigators to prevent their progress and disperse the riot," she said.

The spokeswoman confirmed "five hits" without elaborating.

In a sermon for weekly Muslim prayers at a mosque in Gaza City, Hamas's Gaza chief Ismail Haniyeh said "we are calling for the strengthening and increasing of the intifada."

"It is the only path that will lead to liberation," he said. "Gaza will fulfil its role in the Jerusalem intifada and it is more than ready for confrontation."

Stabbing attacks in the West Bank, Jerusalem and Israel itself along with rioting have raised fears of a third Palestinian intifada, following a first that began in 1987 and a second in 2000.

The two conflicts cost the lives of some 5,000 Palestinians and around 1,100 Israelis.

Islamist movement Hamas rules Gaza, which suffers an Israeli blocakde and is separated from the West Bank. It remains deeply divided from Palestinian president Mahmoud Abbas's Fatah party.

Gaza has been the site of three Israeli offensives since 2008, but had remained mainly calm amid the recent unrest in the West Bank and occupied east Jerusalem until Friday.

Last summer's 50-day Israeli offensive left more than 2,200 people dead and 100,000 homeless.

*This story was edited by Ahram Online.