JERUSALEM, Sept. 28 (Xinhua) -- Israel's air force attacked northern Gaza Strip twice on Friday, in response to demonstrations along the border fence of the Gaza Strip.

Some 20,000 Palestinians gathered in several locations as part of the riots along the Gaza Strip, said the Israel Defense Forces (IDF) in a statement issued on Friday evening.

The Israeli army said that rioters hurled grenades and explosive devices in several locations, lit tires on fire and hurled rocks towards Israeli troops and the security fence. No injuries to Israeli soldiers nor damage were caused.

The IDF troops identified several suspects crossing the security fence from the northern Gaza Strip before immediately returning, said the Israeli army.

In response, Israeli aircraft struck northern Gaza Strip, adding that a Hamas military post was targeted in the second strike in Gaza Strip.

According to the Israeli army, its troops also responded to the violent demonstrations with riot dispersal means and operated in accordance with standard operating procedures.

The Gaza Health Ministry on Friday reported that six demonstrators during the clashes were killed by the Israeli army gunfire, including youths aged 12, 14 and 18. And a total of 506 Palestinians were injured in the clashes, said the ministry.

During the riots, two military drones fell in the southern Gaza Strip. The Israeli army said there was no fear of leakage of information following the incident.

At the same time, 11 fires broke out in the areas of Israeli settlements near the border fence as a result of burning flying balloons sent by the Palestinians.