At least four people have been injured in an explosion at a Hamas training camp in the southern Gaza Strip, according to Palestinian health officials and witnesses.

The blast near the town of Khan Yunis late on Tuesday reportedly destroyed the base and it was still on fire about one hour later.

It was not immediately clear what caused the explosion, but the Israeli military said it was looking into reports of the incident.

Dr Moaiya Hassanain of the Palestinian health ministry told The Associated Press news agency that two of the five wounded were in critical condition.

He said that all five were fighters from the armed wing of the Hamas movement, which seized full control of Gaza last year after pushing out security forces loyal to Mahmoud Abbas, the Palestinian president.

Last weekend, scores of members of Abbas's Fatah party were detained in the Gaza Strip after a bombing killed five Hamas fighters and a young girl.

Hamas said that Fatah carried out the attack to undermine its rule, but Fatah has denied any involvement in the blast and said the attack was part of an internal conflict within Hamas.

Hamas and Israel agreed to a ceasefire in the Gaza Strip last month which saw the Palestinian group halt the firing of rockets and mortars, while Israel stopped raids into the territory.