Four Palestinians were killed and 10 others injured overnight and early on Wednesday in a series of airstrikes and tank shelling by Israel in the Gaza Strip in response to the rockets militants fired into southern Israel, medics and security sources said.

Ashraf al-Qedra, Hamas-run health ministry spokesman in Gaza, told reporters that another Palestinian died on Wednesday east of Rafah town in southern Gaza in an airstrike. Previously, three Palestinians died in raids in the past 24 hours.

Al-Qedra said that since Tuesday night, Israeli warplanes have carried out four airstrikes and seven rounds of artillery shelling on the Gaza Strip, killing four Palestinians and wounding ten others, including a woman and a child.

Hamas security officials said that the four killed were militants, three of them were members of Hamas' armed wing al- Qassam Brigades.

The group and other militants fired over 50 mortars and rockets from Gaza into southern Israel, according to Israeli radio.

Violence in Gaza escalated right after the visit of the Qatari emir and his high-ranking delegation on Tuesday, during which the emir pledged 400 million dollars in aid to help construct the Palestinian enclave.

Fawzi Barhoum, Hamas movement's spokesman said in a press statement that "Hamas condemns the Israeli occupation's aggression and the escalation (of violence) in the Gaza Strip."

"This aggression is a reflection of Israel's outrage toward the historic visit of Qatari Emir Hamad Ben Khalifa al Thani, which was a very successful visit to the Gaza Strip," said Barhoum.

Meanwhile, al-Qassam Brigades vowed revenge after Israel killed its members. Earlier, the group claimed responsibility for the attacks against Israel along with the Popular Resistance Committees (PRC), which is loyal to Hamas.

The Hamas-run ministry of education urged children living along the border with Israel not to go to schools on Wednesday, fearing more Israeli airstrikes are on their way.

The Hamas-run ministry of interior said that Israel has closed the crossing points of Erez and Kerem Shalom respectively in northern and southern Gaza.

The ministry also said that it has given instructions to evacuate a checkpoint just 2 km away from Erez crossing point in northern Gaza Strip.

Since the Israeli military operation on the Gaza Strip in early 2009, the enclave has been witnessing a tit-for-tat violence between its militants and the Israeli army.

The goal of the 2009 operation was to rein in militant groups and prevent them from firing rockets into Israel. A fragile Egyptian-brokered truce was reached between Hamas, rulers of the Gaza Strip, and Israel, which apparently does not hold.