The Islamic Revolutionary Guard Corps warned Israel and the U.S. on Wednesday that if attacks on Lebanon do not stop, it will retaliate and deliver a "regretful response."

"We strongly warn the treacherous American and its Zionist executioner partner that if the aggression against dear Lebanon is not immediately halted, we will fulfill our duty and give a regretful response to the evil aggressors in the region," the IRGC said in a statement, according to the state TV's Telegram channel.

Pakistan's Prime Minister Muhammad Shehbaz Sharif is urging "restraint" amid reports of ceasefire violations, he said in a post on X.

"Violations of ceasefire have been reported at few places across the conflict zone which undermine the spirit of peace process," Sharif said in the post.

"I earnestly and sincerely urge all parties to exercise restraint and respect the ceasefire for two weeks, as agreed upon, so that diplomacy can take a lead role towards peaceful settlement of the conflict," the prime minister added.

Sharif did not say specify where the violations took place.

Sharif tagged accounts for President Donald Trump, Vice President JD Vance, Secretary of State Marco Rubio and others, along with the Iranian president and the Iranian foreign minister.

President Donald Trump said Vice President JD Vance may not attend upcoming negotiations due to “safety, security,” though his exact concerns were not disclosed, he told the NY Post in a phone interview.

“We’ll have Steve Witkoff, Jared Kushner, JD -- maybe JD, I don’t know. There’s a question of safety, security,” Trump reportedly told the NY Post.

Trump also said he expects in-person talks to take place “very soon,” according to the NY Post.

“Very soon, actually — it’s going to take place very soon,” he reportedly said.

Firm plans over upcoming talks have yet to be formally announced, though mediators are planning for the end of the week.

White House press secretary Karoline Leavitt said Wednesday that “there are discussions about in person talks, but nothing is final until announced by the President or the White House.”

The Islamic Revolutionary Guard Corps said in a statement that it intercepted and destroyed a Hermes 900 drone over the central province of Fars, Iran, on Wednesday, according to the semi‑official Fars News Agency.

The incident was reported after Iran’s oil ministry’s news outlet said the country’s Lavan oil refinery was hit by a strike earlier on Wednesday. Israel denied involvement in the Lavan explosion.

-ABC News' Somayeh Malekian

Flags were lowered to half-mast at the Presidential Palace in Beirut and across the country, as Lebanon marked a day of national mourning following Wednesday's Israeli bombardment in Beirut and other parts of the country.

A meeting of President Joseph Aoun's cabinet began with a minute's silence to mark the killings, the president's office said in a post to X.

Lebanon's Ministry of Health said at least 203 people were killed in the attacks, with more than 1,000 people injured. Many funerals are expected to take place in Lebanon on Thursday.

In statements posted to Telegram on Thursday, Hezbollah claimed to have fired rockets toward northern Israel, targeted an Israeli military vessel with an anti-ship missile and launched several attacks on Israeli forces operating in southern Lebanon.

-ABC News' Ghazi Balkiz and Joe Simonetti