GAZA CITY, Palestinian Territories: Three Palestinians were wounded by Israeli gunfire in Gaza, medical sources said, raising to six the number of Gazans injured in unrest on Friday near the enclave's borders.

Gaza health ministry spokesman Ashraf al-Qudra said three men aged 19-21 were moderately wounded by Israeli gunfire east of Jabalia, in northern Gaza.

Israeli military sources said that "Palestinians in the northern Gaza Strip fired and damaged a military vehicle."

"In addition, during the course of the day Palestinians gathered adjacent to the security fence, hurling firebombs and rocks at soldiers," which the army regarded as "serious events that threaten the security and stability in southern Israel."

The military sources said that Israeli soldiers shot towards "instigators of violence."

Earlier on Friday, Qudra said three Gaza farmers were wounded by Israeli tank fire east of El-Bureij, near central Gaza's border with the Jewish state.

An Israeli army spokesman said they were aware of the explosion, but that it was probably a "work accident" or a bomb left by Palestinians, and not the result of Israeli fire.

Four Palestinians have been killed by Israeli gunfire and over 100 wounded since the November 21 ceasefire between the Jewish state and Gaza's Hamas rulers, according to the latest report of the UN Office for the Coordination of Humanitarian Affairs (OCHA).

Under the terms of the Egyptian-mediated truce, Palestinians are supposed to have access to arable land in a buffer zone up to 100 metres (yards) from the border fence.

Israel allows "civilian access on foot to areas up to 100 meters from the perimeter fence for agricultural purposes only, and vehicular access to a distance of 300 meters," the OCHA report states.