Iran's Supreme Leader Ayatollah Ali Khamenei said in a statement read by a television presenter on Wednesday that his country will not accept President Donald Trump's call for an unconditional surrender.

In his first remarks since Friday, when he delivered a speech broadcast on state media after Israel began bombarding Iran, Khamenei said peace or war could not be imposed on the Islamic Republic.

"Intelligent people who know Iran, the Iranian nation, and its history will never speak to this nation in threatening language because the Iranian nation will not surrender," he said.

"The Americans should know that any U.S. military intervention will undoubtedly be accompanied by irreparable damage."

Thousands of people were fleeing Tehran on Wednesday after Israeli warplanes bombed the city overnight, and a source said Trump was considering options that include joining Israel in attacking Iranian nuclear sites.

Israel's military said 50 Israeli jets had struck around 20 targets in Tehran overnight, including sites producing raw materials, components and manufacturing systems for missiles.

A source familiar with internal discussions said Trump and his team were considering a number of options, which included joining Israel in strikes against Iranian nuclear sites.

Iran had conveyed to Washington that it would retaliate against the United States for any direct participation, its ambassador to the United Nations in Geneva, Ali Bahreini, said. He said he already saw the U.S. as "complicit in what Israel is doing."