Trump says damage to Iran's nuclear sites is 'far below ground level'

There was no formal "Gang of Eight" briefing for the top leaders of the House and the Senate before the U.S. launched strikes on Iran on Saturday, sources told ABC News, but top Republican members were given details ahead of the action.

Both House Speaker Mike Johnson and Senate Majority Leader John Thune were briefed on the military action before the strikes were carried out, according to people familiar with those conversations.

Democratic leaders -- House Minority Leader Hakeem Jeffries and Senate Minority Leader Chuck Schumer -- were notified of the strike but not given any details, per sources.

One of those sources believed the Democratic leaders were informed only after the military action was underway.

Schumer's spokesperson later told reporters the message came "shortly ahead" of President Donald Trump's announcement, describing it as "a perfunctory notification without any details."

-ABC News' Rachel Scott, Lauren Peller and Allison Pecorin

Iranian dissident groups have responded to the U.S. strikes on Iran's key nuclear sites by reiterating their calls for the toppling of the Islamic Republic and its leader, Ayatollah Ali Khamenei.

Reza Pahlavi, the son of the last Shah Mohammad Reza Pahlavi who was deposed by the 1979 Iranian Revolution, said in a post to X that the American attacks "are the result of the regime's catastrophic pursuit of nuclear weapons at the expense of the Iranian people."

"As Khamenei considers how to respond from his underground bunker, I say to him: For the sake of the Iranian people, respond by stepping down, so the proud Iranian nation can leave the disastrous period of the Islamic Republic behind and start a new chapter of peace, prosperity and greatness," Pahlavi wrote.

Maryam Rajavi, the president-elect of the National Council of Resistance of Iran -- a coalition of dissident Iranian groups that grew out of the People's Mojahedin Organization of Iran, or MEK, revolutionary group that fought against the shah and the Islamic Republic -- said in a statement sent to ABC News, "Now Khamenei must go."

"Khamenei is responsible for an unpatriotic project that, in addition to costing countless lives, has cost the Iranian people at least two trillion dollars -- and now, it has all gone up in smoke," she said.

"No to war -- yes to regime change, i.e., changing the religious dictatorship by the Iranian people and the Iranian Resistance," Rajavi added. "Forward toward a free Iran and a democratic, non-nuclear republic with separation of religion and state and gender equality."

An Israeli military official told ABC News that Iran fired between 20 and 30 ballistic missiles toward Israel on Sunday morning following the American strikes on three Iranian nuclear sites late on Saturday.

-ABC News' Jordana Miller and Dada Jovanovic

British Prime Minister Keir Starmer and European Union foreign affairs chief Kaja Kallas said in statements to X on Sunday morning that Iran cannot be allowed to create nuclear weapons, while also urging de-escalation and diplomacy to end the spiraling Middle East crisis.

"Iran's nuclear program is a grave threat to international security," Starmer wrote in his statement. "Iran can never be allowed to develop a nuclear weapon and the U.S. has taken action to alleviate that threat."

"The situation in the Middle East remains volatile and stability in the region is a priority," Starmer added. "We call on Iran to return to the negotiating table and reach a diplomatic solution to end this crisis."

Kallas said Iran "must not be allowed to develop a nuclear weapon, as it would be a threat to international security."

"I urge all sides to step back, return to the negotiating table and prevent further escalation," she added.

French Foreign Minister Jean-Noel Barrot, meanwhile, also said Paris "has repeatedly expressed its firm opposition to Iran gaining access to nuclear weapons," though said France reacted to news of the U.S. strikes "with concern." He added, "France was not involved in these strikes, nor in their planning."

"France is convinced that a lasting solution to this issue requires a negotiated solution within the framework of the Non-Proliferation Treaty on nuclear weapons," Barrot added.

-ABC News Dada Jovanovic and Tom Soufi Burridge