Three Palestinian fighters have been killed after a series of explosions near the southern Gaza Strip town of Khan Younis, witnesses and officials said.

It was not immediately clear what caused the blasts on Wednesday, but officials swiftly ruled out the possibility of an Israeli airstrike.

Ashraf al-Qedra, a spokesperson for Gaza's Health Ministry, said a blast at a training site for a Palestinian resistance group killed three people and wounded five. But witnesses said the explosions occurred in a house, not at a training site.

Shehab, a Gaza-based news agency and a mouthpiece for the ruling faction Hamas, said the dead were members of the Hamas armed wing, Izz al-Din al-Qassam Brigades.

Among the wounded were firefighters who rushed to the scene after the first blast.

Police imposed a security cordon around the blast site, while Eyad Al-Bozom, an Interior Ministry spokesperson, said in a statement that an investigation was underway into the circumstances of the explosions.

Also on Wednesday, Hamas Prime Minister Ismail Haniya called on Egypt to open its borders with Gaza for the movement of people and goods.

"Out of love and the endorsement of the historical role of our brothers in Egypt, we call on Egypt to reopen Rafah crossing point and constantly let everything in for Gaza," Haniya said as he visited the sites of construction projects funded by Qatar.

Materials for the projects - which include a new housing complex, a hospital and the rehabilitation of major roads - come through Rafah crossing point, but they are delivered only when the crossing is open.

Egypt keeps has kept the crossing mostly closed since the ouster of President Mohammed Morsi last summer.

PHOTO CAPTION

Hamas militants take part in a funeral of three comrades who were killed in an explosion, in the al-Nusairat refugee camp, in central Gaza Strip, on April 16, 2014.

Aljazeera