JERUSALEM, March 31 (Xinhua) -- Israeli military on Saturday warned of an expanded military operation against Hamas if violence on the border with Gaza continues.

Israeli Military spokesman Brigadier General Ronen Manelis said in a briefing to journalists hours after a Palestinian protest turned violent on Israel's southern border.

Tens of thousands of Palestinians participated in the demonstration on Friday, as Israeli Jews marked the holiday of Passover.

Fifteen Palestinians were reportedly killed from Israeli fire. The Israeli military spokesman said they were all men and the majority of them were militants.

The Palestinian Health Ministry reported 1,000 injuries by live fire, rubber bullets and tear gas.

"The State of Israel cannot and will not allow this to continue," said Manelis, adding "We will be forced to respond within the Gaza Strip."

Until now, after weeks of violent exchanges between Hamas and the Israeli military, Israel's actions were limited to airstrikes against Hamas military installments.

Gaza militants have been increasing their actions in the border area. Manelis said the army knew four bombs which were planted along the border yesterday.

Violence is expected to continue before May 15, the Palestinians' Nakba Day, or known as the day of their catastrophe, which coincides with Israel's 70th Independence Day.