Thousands of Palestinian demonstrators clashed with Israeli troops at a West Bank checkpoint on Friday as hundreds more gathered by Jerusalem's Old City to mark Land Day.

Rallies were also held by refugee communities in neighbouring Jordan and Lebanon to mark the annual event that commemorates the deaths of six Arab Israeli protesters at the hands of Israeli forces during mass demonstrations in 1976 against plans to confiscate Arab land in Galilee.

Tensions were high at the Qalandia checkpoint, just north of Jerusalem, as a handful of masked Palestinian youths hurled rocks and set tyres alight, with Israeli troops firing a barrage of teargas, rubber bullets and stun grenades to break up the protest.

Troops also fired a foul-smelling liquid called "skunk" into the crowd, an AFP correspondent said. By 1100 GMT, around 30 people had been treated for teargas inhalation, Palestinian medics said.

At least a dozen rallies were held across Israel and the occupied territories, with demonstrators also marching towards the Israeli border in Lebanon and Jordan.

"There is a riot taking place at Qalandia. Rioters are throwing stones at the IDF (Israel Defence Force) and burning tyres, and the IDF is responding with riot dispersal means," a military spokesman told AFP.

In annexed Arab east Jerusalem, around 400 demonstrators waving huge Palestinian flags gathered outside the Old City near Damascus Gate, sparking scuffles with hundreds of watching police, an AFP correspondent said. Police said they had made several arrests.

Another hundred or so people gathered by Lion's Gate, where police arrested four people, and another two were treated by medics after being injured by police batons, another AFP correspondent said.

In Lebanon, to the north, hundreds of Lebanese and Palestinian refugees gathered near the historic Beaufort Castle.

"Jerusalem, here we come," roadside banners proclaimed. "Land Day is the day when we rededicate ourselves to the right of return," claimed by the diaspora communities but rejected by Israel.

The main Land Day march was to take place from 1230 GMT in the Arab Israeli town of Deir Hanna in Galilee, with another march scheduled in the southern Negev desert.

In anticipation of mass protests, the Israeli army imposed a 24-hour closure on the occupied territories late on Thursday, barring Palestinians from entering Israel excepted for humanitarian reasons or medical emergencies.

Israeli police chief Yohanan Danino urged Arab community leaders to "prevent extremists from causing provocations."

Police also imposed an age limit on worshippers attending the main weekly Muslim prayers at the flashpoint Al-Aqsa mosque compound in Jerusalem's Old City, barring all men except residents over the age of 45. There was no restriction on women.

Israel is hoping to avoid the bloody confrontations that took place last May when thousands gathered along Israel's borders with Lebanon and Syria on Nakba Day to protest on the anniversary of Israel's creation in 1948.

Troops opened fire on protesters trying to breach the armistice line from Syria and Lebanon, killing 11 and wounding hundreds, according to UN figures. More than 120 people were also injured by gunfire in similar protests in northern Gaza.

A month later, at least 10 people were killed and hundreds injured in the occupied Golan Heights when Syrian protesters tried to cross onto the Israeli side on Naksa Day, which marks the anniversary of the 1967 Six Day-War, when Israel seized the territories.

On Friday, police and soldiers in the Golan were deployed next to the Kuneitra crossing and in the Majdal Shams area, while along the Lebanese border, forces fanned out around the Metulla crossing, press reports said.

Troops were also deployed in the Jordan Valley where thousands protested near the Allenby Crossing.

More than 15,000 people, including opposition Islamists and trade unionists as well as Palestinians, gathered for a sit-in in Kafrein some 10 kilometres (six miles) from the crossing and barely a kilometre and a half (a mile) from the frontier.

"Security presence is normal. It's a peaceful sit-in and everything is under control," a security official in Jordan told AFP.