Palestinian demonstrators clashed with Israeli security forces in the West Bank and east Jerusalem during anti-settlement protests after the Muslim Friday prayers.
In Israeli-annexed east Jerusalem, troubles broke out in the Shuafat Palestinian refugee camp, where AFP photographers saw youths throw stones at police who responded with massive volleys of tear-gas grenades.
Witnesses saw plainclothes policemen grab six youngsters and remove them from the scene.
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There were also skirmishes in the city's Issawiya neighbourhood.
Some of the fiercest confrontations were at Qalandia, the main crossing point between Jerusalem and the city of Ramallah where the Palestinian Authority has its headquarters.
Six Palestinians injured
Staff at a Ramallah hospital said six Palestinians were injured in those clashes, one of them in critical condition with a gunshot wound to the chest.
Qalandia, where east Jerusalem meets Palestinian Authority territory, is guarded on the Israeli side by a combination of police, troops and civilian contractors.
A military spokeswoman said she had no knowledge of Israelis opening fire there. The Jerusalem police spokesman could not immediately be reached for comment on Friday evening, the start of the Jewish sabbath.
In the West Bank city of Hebron, about 300 protesters chanted "Thousands of martyrs march to Jerusalem" and several of them hurled rocks at security forces who responded with tear gas.
In Dir Nizam, near Ramallah, about 100 Palestinians hurled rocks at soldiers, slightly injuring one, the military said. An army statement said three alleged rioters were detained for questioning.
Police on high alert
Similar confrontations took place at Bilin and Nilin, sites of weekly Palestinian protests against Israel's West Bank "security barrier."
Police were also on high alert inside Jerusalem where authorities again prevented men under 50 from attending Friday prayers at the flashpoint Al-Aqsa mosque compound.
Police spokesman Micky Rosenfeld said prayers at the compound passed without incident and Jerusalem was generally calm.
An already charged atmosphere intensified this week as a rebuilt 17th-century synagogue was opened in the Jewish quarter of the Old City, a few hundred metres (yards) from the compound.
Many Palestinians view Israeli projects near the mosque compound -- a site holy both to Jews and Muslims -- as an assault on its status quo.
Rallies held in Gaza
Friday's biggest rallies were in the Gaza Strip, where there had been calls for protests by the militant Islamist movement Hamas, which rules the territory, and by Islamic Jihad.
More than 10,000 people, among them about 400 masked but unarmed activists, demonstrated in the strip's central area and another 2,000 in the southern town of Rafah, according to an AFP journalist.
Warplanes hit the disused Gaza airport in the south of the coastal strip late Friday night and Palestinian medical officials said 11 people in the vicinity were hurt, although only two were described as in serious condition.
It was the second night of Israeli raids since a rocket fired from the Gaza Strip killed a worker on an Israeli farm on Thursday. A second rocket on Thursday landed harmlessly on open ground.
Another rocket was fired into Israel earlier on Friday but caused no injuries.
The cross-border exchanges came as UN Secretary-General Ban Ki-moon was headed for a weekend visit to Gaza, the West Bank and Israel and as the United States sought to get Palestininans and Israelis talking peace.
