The Israeli military says Palestinian militants in the Gaza Strip have fired a rocket into southern Israel, amid a sharp increase in tensions.

A statement said sirens were triggered in Israeli communities near the border but the rocket landed in open countryside and no-one was hurt.

Earlier, six Palestinians were shot dead near the border fence with Gaza.

There has been a spate of attacks and confrontations between Palestinians and troops in recent days.

The military statement said the rocket was believed to have landed in a field not far from the border early on Saturday.

Gun and knife attacks by Palestinians have left four Israelis dead and many wounded since last weekend, while at least three Palestinians have been killed during clashes with security forces in the West Bank and East Jerusalem.

Ismail Haniyeh, the leader of Hamas which runs Gaza, said a new intifada - or uprising - was under way, although the BBC's Yolande Knell in Jerusalem says the scale of violence does not yet amount to that.

Palestinian medical sources said the six Palestinians were shot dead and many others wounded in two separate incidents in Gaza on Friday when Israeli troops opened fire.

The Palestinians had been protesting in solidarity with Palestinians in Jerusalem and the West Bank.

The Israeli military said more than 1,000 rioters had massed at the border fence, throwing a grenade and rocks, and rolling burning tyres at Israeli forces.

After firing warning shots, troops fired towards the "main instigators" to disperse the riot, a military statement said.

In Israel on Friday, police reported an apparently "nationalistic" attack by an Israeli, who they say stabbed two Israeli Bedouins and two Palestinians.

The attack in the southern city of Dimona was apparently in retaliation for stabbing attacks on Israeli Jews this week. The suspect was arrested.

On Friday, Israeli Prime Minister Benjamin Netanyahu said he "strongly condemned the harming of innocent Arabs" and vowed to bring to justice anyone who breaks the law.

Shortly afterwards, an attacker was shot dead after stabbing an Israeli policeman near Hebron.

In Jerusalem, a 16-year-old ultra-Orthodox Jewish Israeli was stabbed and wounded. A Palestinian suspect fled but was caught by police.

An Israeli policeman, meanwhile, was injured and his assailant shot dead near the Jewish settlement of Kiryat Arba, close to Hebron. Separately, a Palestinian woman was shot and wounded after trying to stab a guard at a bus station in Afula, northern Israel, police said

Violence between Israelis and Palestinians have risen since clashes erupted at a flashpoint holy compound in East Jerusalem last month.

An Israeli couple were shot dead in the West Bank in front of their four children, while two more Israelis were killed in a stabbing in Jerusalem's Old City days later - the first in a spate of stabbings of Israelis in the city, northern and western Israel and the West Bank.

Hundreds of Palestinians have been wounded and at least three, including a 13-year-old boy, shot dead in clashes in the West Bank and East Jerusalem during the same period.

Five of the Palestinians who apparently carried out the stabbings have been killed.

Israel has increased security across the country and imposed temporary restrictions on Palestinians seeking to enter the Old City of Jerusalem.