The Israeli army began pumping seawater into Gaza’s tunnels on Tuesday, US media reported, a measure that could cause long-term environmental damage to the besieged territory.
The Wall Street Journal (WSJ) reported the process would likely take weeks, while Palestinians and Israelis said it risks the lives of hostages being held by Hamas and could constitute a war crime.
ABC News reported that the flooding appears to be limited as Israel evaluates the strategy's effectiveness.
No more information was provided and there was no comment from the Israeli army.
Earlier this month, WSJ, citing US officials, reported that Israel assembled a large system of pumps that may be used to flood tunnels used by the Palestinian Hamas group under the Gaza Strip in a bid to drive out fighters.
Around mid-November, Israel's army completed the set-up of at least five pumps about a mile north of the Al-Shati refugee camp that could move thousands of cubic meters of water per hour, flooding the tunnels within weeks, the report said.
Some officials in Washington have expressed support for such a move. But it has raised concerns that the flooding could potentially kill Israeli hostages captured by Hamas during its 7 October attack in southern Israel.
But US President Joe Biden said Tuesday he could not confirm whether any of those captives, which include Americans, remain in the tunnel system.
"With regard to the flooding of the tunnels, there are assertions being made that they [Israel] are quite sure there are no hostages in any of these tunnels. But I don't know that for a fact," Biden said.
Dubbed the , most of the tunnels date back to the 1980s when they were used to smuggle goods under the newly divided city of Rafah.
The network became more important, and advanced, following the tightening of Israel’s blockade in 2007, which cut Gaza off from the world.
There are concerns that the seawater, if flushed into the tunnels, would endanger what’s left of Gaza’s already highly salinised water supply, and result in irreversible environmental damage, possibly amounting to another war crime.
There have already been international calls to put Israeli officials on trial over 'genocide' in the Palestinian enclave.
Israel’s unprecedented bombardment has killed more than 18,400 people, most of them women and children, Gaza's health ministry has said.
The war has obliterated much of Gaza’s infrastructure, with destruction worse than that seen in Germany in the Second World War, according to the EU's top diplomat, Josep Borrell.