Four people reported killed on Syrian border and six reported killed on Lebanon border as thousands of protesters try breach the frontiers.

Israeli gunfire killed six people and wounded 71 others on the border in south Lebanon during a Palestinian refugee protest on Sunday to mark "Nakba Day," a local medical source said.

Among the wounded, thirteen are in critical condition.

The UN peacekeeping force in the border region called for "maximum restraint on all sides in order to prevent any further casualties" and "immediate concrete security steps on the ground" to prevent any further bloodshed.

On the other side of the border, Israeli gunfire killed four protesters and wounded more than sixty others as civilians crossed from Syria onto the annexed Golan Heights on Sunday, sparking a war of words between Damascus and Jewish state.

Four people were killed and four others critically hurt by Israeli gunfire after protesters from a Syrian-held part of the Golan entered the annexed territory, a doctor who treated casualties said.

Troops fired live rounds and tear gas at the protesters who suddenly burst through to Israeli-held territory rather than demonstrating alongside the border fence as they have in past years on the anniversary of Israel's 1948 creation.

The unrest came as Palestinians in the occupied territories, inside Israel and across the region marked the anniversary of the Jewish state's 1948 creation, known in Arabic as the "nakba" or "catastrophe."

As a result, Israeli Occupation Forces declared the area a "closed military zone" in retaliation to the events taking place at the border.

"Civilians breached the Israel-Syria border near the Israeli village of Majdal Shams," the Israeli military said. "Forces opened fire in order to prevent the violent rioters from illegally infiltrating Israeli territory.

"From initial reports, there are dozens of injured," it said in a statement.

Syria's foreign ministry, meanwhile, condemned Israel for opening fire on protesters on the Golan, in south Lebanon and Gaza, warning that the Jewish state would bear full responsibility.

"We firmly denounce the criminal Israeli actions against our people in the Golan Heights, Palestine and southern Lebanon that left several people dead and wounded," the foreign ministry said.

A Palestinian throwing a stone at Israeli security forces during clashes at Qalandiya checkpoint, near the West Bank city of Ramallah on Nakba Day, May 15, 2011

"Israel will have to bear full responsibility for its actions."

An Israeli official also pointed the finger at Assad's regime, which has been rocked by two months of pro-reform protests inspired by Arab revolts which have ousted strongmen in Tunisia and Egypt.

"This appears to be a cynical yet transparent act by the Syrian regime to create a crisis on the border in order to distract attention from the very real problems that regime faces at home," he said, on condition of anonymity.

Channel 1 television said its correspondent in Majdal Shams, a Druze town on the Golan, said he had come across 30-40 infiltrators in its main square, some of who said they were Palestinians from Yarmuk refugee camp in Damascus.

The army sealed off the town and its immediate surroundings and carried out house-to-house searches for infiltrators, defense sources said.

This Nakba Day is considered a pivotal incident along the 1974 truce line, especially when organizers speak of breaking the barrier of fear en route to returning to Palestine.