The Israeli army says 24 of its soldiers were killed in Gaza on Monday - the deadliest day for its forces since their ground operation began.

That includes 21 reservists who died in an explosion likely caused by mines that Israeli forces had placed in two buildings to demolish them, the Israel Defense Forces (IDF) said.

It is thought a missile fired by Palestinian armed fighters hit a tank guarding the troops just beforehand and the tank instantly fires directly into the building which Israeli forces had placed mines to demolish.

The IDF is investigating what happened.

The IDF's chief spokesman, Rear Admiral Daniel Hagari, said the reservists were killed in central Gaza at around 16:00 (14:00 GMT) on Monday - close to the kibbutz of Kissufim on the Israeli side of the border.

The first funerals for those killed in the explosion have been held at Mount Herzl in a rainy Jerusalem.