Iran's claim to have successfully launched a rocket into space has been undermined by doubts over the monkey it says travelled on board on the mission.

Tehran trumpeted its success in launching the Kavoshgar rocket 75 miles above the earth, complete with primate, in a capsule named Pishgam, or Pioneer.

The launch caused immediate alarm in Israel, with Iran appearing to have struck the first blow in a feared Middle East space race, defying international sanctions to develop technology that could be used in nuclear warheads.

But images released before and after the launch suggest the hardline Islamic state may simply have been monkeying around.

Photographs taken before the launch showed a light-furred animal with a distinctive red mole above its right eye. But the monkey that 'returned' had dark fur, and no mole.

While footage of the rocket launch had been widely distributed, there was no evidence to show the rocket had returned to earth, observers noted.

Iranian defence minister Ahmad Vahidi marked the launch, on the 34th anniversary of the Islamic Revolution, saying: "This success was the first step towards man conquering space and it paves the way for other moves.

"The monkey which was sent in this launch landed safely and alive and this is a big step for our experts and scientists."

But Yariv Bash, founder of Space Israel, which is developing an unmanned Israeli spaceship to fly to the moon, said the pictures showed Tel Aviv had less to fear than initially feared.

"It looks like a very different monkey - the nose, the features, everything is different," said Bash. "This means that either the original monkey died from a heart attack after the rocket landed, or that the experiment didn't go that well."