DUBAI (AP) - A rocket at an Iranian space centre that was to conduct a satellite launch criticised by the US apparently exploded on its launch pad on Thursday (Aug 29), satellite images show, suggesting the Islamic Republic suffered its third failed launch this year alone.

State media and officials did not immediately acknowledge the incident at the Imam Khomeini Space Centre in Iran's Semnan province.

However, satellite images by Planet Labs showed a black plume of smoke rising above a launch pad there, with what appeared to be the charred remains of a rocket and its launch stand. In previous days, satellite images had shown officials there repainted the launch pad blue.

On Thursday morning, half of that paint apparently had been burned away.

"Whatever happened there, it blew up and you're looking at the smouldering remains of what used to be there," said David Schmerler, a senior research associate at the Middlebury Institute of International Studies.

Schmerler told The Associated Press that the images of the space centre suggested that the rocket either exploded during ignition or possibly briefly lifted off before crashing back down on the pad. Water runoff from the pad, likely from trying to extinguish the blaze, could be seen along with a host of vehicles parked nearby.

NPR first reported on the satellite images of the apparent failed launch at the space centre, some 240km southeast of Iran's capital, Teheran.

Iranian satellite launches had been anticipated before the end of the year.

In July, Iran's Information and Communications Technology Minister Mohammad Javad Azari Jahromi told the AP that Teheran planned three more launches this year, two for satellites that do remote-sensing work and another that handles communications.

The Nahid-1 is reportedly the telecommunication satellite, which authorities plan to have in orbit for two-and-a-half months. Nahid in Farsi means "Venus." The satellite, which had Iran's first foldable solar panels, was supposed to be in a low orbit around the Earth for some two-and-a-half months.

The semi-official Mehr news agency quoted Jahromi on Aug 13 as saying that the Nahid-1 was ready to be delivered to Iran's Defence Ministry, signalling a launch date for the satellite likely loomed. Iran's National Week of Government, during which Tehran often inaugurates new projects, began Aug 24.

Earlier on Thursday, Iran's Defence Minister, General Amir Hatami, told the state-run IRNA news agency that the country's satellite activities were "being done in a transparent way," responding to AP and other foreign media reporting on activity at the space centre.

"Whenever activity and research bear successful results, we will announce the good news," Hatami said. Iran at times in the past hasn't acknowledged failed launches.

The apparent attempt to launch the Nahid-1 comes after two failed satellite launches of the Payam and Doosti in January and February. A separate fire at the Imam Khomeini Space Centre in February also killed three researchers, authorities said at the time.

Over the past decade, Iran has sent several short-lived satellites into orbit and in 2013 launched a monkey into space.

The US alleges such launches defy a UN Security Council resolution calling on Iran to undertake no activity related to ballistic missiles capable of delivering nuclear weapons.

Iran, which long has said it does not seek nuclear weapons, maintains its satellite launches and rocket tests do not have a military component. Teheran also says it doesn't violate the UN as it only "called upon" Teheran not to conduct such tests.

The tests have taken on new importance to the US amid the maximalist approach to Iran taken by President Donald Trump's administration. Tensions have been high between the countries since Trump unilaterally withdrew the US from Iran's nuclear deal over a year ago and imposed sanctions, including on Iran's oil industry. Iran recently has begun to break the accord itself while trying to push Europe to help it sell oil abroad.

The State Department did not immediately respond to a request for comment.