"I regret that despite my repeated urgings, and those of many regional and world leaders together, an already dangerous conflict has now escalated even further," Ban told reporters.

The UN chief described as "appalling" the death of four boys killed by Israeli strikes Wednesday on a Gaza City beach.

"I urge Israel to do far more to stop civilian casualties. There can be no military solution to this conflict," he said.

Israel began a ground operation in Gaza on Thursday, on the 10th day of an offensive to stamp out rocket fire from the Hamas-run enclave that has had a heavy toll on Palestinian lives.(KH/SI)