Iranian President Masoud Pezeshkian delivered a defiant address at the United Nations General Assembly on Wednesday, accusing the United States and Israel of carrying out attacks against Iran and declaring that his country had been the "victim of terrorism."

His speech came a day after US President Donald Trump used the same UN platform to defend Washington's military campaign against Iran and warned that he could "annihilate" the Islamic Republic if a deal was not reached.

Pezeshkian holds up photos of Khamenei, schoolchildren

During his address, Pezeshkian held up photographs of Iran's late Supreme Leader Ayatollah Ali Khamenei, who Iran says was killed in the opening US-Israeli strikes on February 28, as well as images of children killed in a school strike.

"The US president called us terrorists. We have been the victims of terrorism," Pezeshkian said.

"I come from an Iran where our esteemed Supreme Leader was assassinated without any legal justification or reason. I come from Iran where a school was bombed," he added.

Pezeshkian said more than 150 Iranian children were killed in the early days of the conflict.

A UN-backed fact-finding mission has separately said there were reasonable grounds to believe the US was responsible for the Minab school strike, while Washington has rejected the findings.

'We did not bend the knee'

The Iranian president said Tehran had responded to the US and Israeli attacks with what he described as the "utmost strength," framing Iran's military actions as self-defence.

"We have only defended ourselves. We are not terrorists," Pezeshkian said, according to reports of his speech. He added that Iran would not surrender despite military pressure.

Addressing Trump directly, Pezeshkian said Iran remained open to diplomacy and negotiations but would not accept what he called the "language of force."

He also warned that increased sanctions and pressure would not force Iran to capitulate.

"The resistance of the Iranian people will only increase in the face of sanctions, increased pressure, increased bullying. We will never bow our heads or bend the knee," he said.

US delegation walks out

The speech also triggered a visible diplomatic response inside the UN General Assembly hall.

The US delegation walked out as Pezeshkian spoke about civilian casualties and accused Washington and Israel of targeting Iranian civilians.

The exchange came amid continued diplomatic contacts between Washington and Tehran. US Secretary of State Marco Rubio said Wednesday that any agreement with Iran would require sustained negotiations, while Iranian officials have also indicated that Tehran remains open to diplomacy under certain conditions.