MOSCOW, April 23 (RIA Novosti) -- Israeli commanders have threatened to launch a military operation in Gaza if Palestinian militants fail to stop firing rockets at Israel within 24 hours, the Palestinian Information Center said.

The center said Israeli aviation had airdropped leaflets with the ultimatum in Gaza Sunday night, and reported a substantial build-up of Israeli military equipment, including tanks and helicopters, on the Gaza border. Witnesses said small Israeli units had already crossed the Palestinian border.

Israel has rejected the Arab world's demands that it withdraw from the West Bank, the Golan Heights and East Jerusalem, which has been proposed as the Palestinian National Authority's (PNA) capital, but hailed the initiative, first advanced in 2002, as an opportunity for dialogue with moderate Arab governments.

A new wave of violence in the area was sparked by the abduction of an Israeli corporal, Gilad Shalit, in June. As three Palestinian militant groups claimed responsibility for the incident, Israel sent troops into Gaza to secure the corporal's release.

The PNA is demanding that Israel release more than 300 Palestinian prisoners, including high-ranking activists of Palestinian groups serving terms for terrorism, in exchange for the corporal.