The United Nations on Friday cited witnesses saying Israeli forces moved about 110 Palestinians into a house, told them to stay inside, and later shelled it repeatedly, killing about 30 people.

The Israeli army said it had no knowledge of such an incident but was investigating.

The UN report said that "according to several testimonies, on 4 January Israeli foot soldiers evacuated approximately 110 Palestinians into a single-residence house in Zeitun (half of whom were children) warning them to stay indoors. Twenty-four hours later, Israeli forces shelled the home repeatedly, killing approximately 30."

The UN Office for the Coordination of Humanitarian Affairs (OCHA) called the events in the Gaza City neighbourhood "one of the gravest incidents since the beginning of operations" by Israeli forces in Gaza on December 27.

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"Those who survived and were able walked two kilometres to Salah Ed Din road before being transported to hospital in civilian vehicles. Three children, the youngest of whom was five months old, died upon arrival at the hospital," OCHA said.