Qatar confirmed that its emir will visit the Gaza Strip on Tuesday, on the first such visit by an Arab head of state since the Islamist Hamas seized control of the coastal enclave in 2007.

Sheikh Hamad bin Khalifa al-Thani "will make a brief visit to the Gaza Strip to inaugurate a number of projects funded by Qatar as part of its efforts to rebuilt the Strip," Qatar's official QNA news agency said on Monday.

Israeli air strikes killed two Gaza fighters on Monday as they clashed with troops who crossed the border on the eve of a landmark visit by the Qatari emir, medical sources said.

The flareup provoked threats of revenge from the Ezzedine al-Qassam Brigades, the armed wing of the ruling Hamas movement, and a pledge from Israeli Prime Minister Benjamin Netanyahu that there would be no immunity for those firing on the Jewish state.

Israeli troops on Saturday boarded a boat carrying pro-Palestinian MPs and activists seeking to run its naval blockade on the Gaza Strip, blocking the latest attempt to reach the enclave by sea, the military said.

The operation, which the military said was concluded peacefully, ended the latest bid by activists to breach Israel's tight maritime embargo on Gaza which prohibits all naval traffic in and out of the Palestinian coastal territory.

The Israeli airforce carried out a sortie in the Gaza Strip early Thursday morning, sources on both sides said, hours after rockets from the enclave hit southern Israel.

Palestinian medics and security sources said the strike targeted a Hamas security site south of Gaza City. They said the attack resulted in no injuries.

Palestinian militants in the Gaza Strip fired a rocket into southern Israel on Wednesday, but it fell on open ground close to the border, Israeli police said.

"No injuries or damage were caused," police spokesman Micky Rosenfeld told Agence France Presse.

Israeli airplanes carried out a sortie in the Gaza Strip early Wednesday morning, the army said, hours after a rocket from the enclave exploded in southern Israel.

Military "aircraft targeted a terror activity site in the northern Gaza Strip. A direct hit was confirmed," a statement read.

Two men were killed and another two critically wounded on Sunday in an Israeli strike on central Gaza, Palestinian medics said in what was the third deadly raid in 24 hours.

The incident occurred just east of Deir al-Balah, with the Israeli military confirming it had targeted "a terrorist rocket squad."

A leader of a hardline Islamist group that has claimed a spate of rocket attacks on Israel in recent days was among three Palestinians killed in Israeli air strikes on Gaza, sources on both sides said on Sunday.

Sheikh Hisham al-Saedini, 43, also known as Abu al-Waleed al-Maqdisi, one of the founding members of Salafist group the Mujahedeen Shura Council, was killed in a strike late on Saturday on the north Gaza town of Jabaliya, Palestinian security sources said.

Israel has warned Finland that it will stop a boat with pro-Palestinian activists on board by force if it tries to break the blockade of the Gaza Strip, a foreign ministry spokesman said Saturday.

"The foreign ministry has been informed by Israel that it would intervene if the ship Estelle which is flying the Finnish flag tries to break (Israel's) blockade against Gaza from the sea," spokesman Risto Piipponen said on state television.

The Israeli Air Force early Thursday morning launched a strike against what a spokeswoman called "a terror activity site" in the northern Gaza strip, which she said was in response to earlier rocket attacks on Israel.

Palestinian officials in Gaza said the target was a training camp of Ezzedine al-Qassam Brigades and said there were no casualties.