Iran's national internet connectivity has collapsed to just 4% of ordinary levels, network monitoring group NetBlocks confirmed on February 28, as US and Israeli military strikes continued across the country and authorities moved to cut off communications.

NetBlocks said in an earlier update that connectivity in parts of Iran including Tehran had already dropped to 54% of ordinary levels, adding that the disruption "will limit visibility into incidents on the ground."

The subsequent near-total blackout matches measures used during last year's conflict with Israel, the organisation said.

Mobile phone lines and text messaging services were also being progressively cut across Iran, Iranian media reported on February 28.

The communications shutdown comes as explosions continued to be reported across Tehran, Isfahan and Qom following the launch of joint US-Israeli operations earlier in the day.

Telephone lines are also reportedly down in recent minutes, according to those who are trying to reach people in Tehran, IntelliNews has learned.

Iran had already closed its entire airspace, suspended trading on the Tehran Stock Exchange and seen the rial plunge to a record low of IRR1,749,500 against the dollar on the free market.

Iranian police earlier declared the situation under control and urged citizens not to be concerned, while authorities denied social media reports that President Masoud Pezeshkian had been killed.

Reza Pahlavi, the son of Iran's last shah, issued a statement urging Iranians to remain at home but prepare for what he called a final act to reclaim the country, warning that if internet and satellite services were disrupted, he would communicate via radio.

This story is developing.