Russia plans to restart launches of its Proton-M rocket in September, a top space official said Monday, ending a freeze that was introduced when one of the carrier rockets crashed in July.

In one of Russia's worst space failures of recent years, a Proton-M rocket carrying navigation satellites exploded shortly after takeoff on July 2. All scheduled launches were then shelved pending an investigation.

"The first launch will take place when we have carried out all the necessary planned work, provisionally this will be in September," the deputy head of the Russian space agency, Alexander Lopatin told journalists, quoted by the RIA Novosti news agency.

The exact date will depend on the recommendations of the commission investigating the accident, he added. The commission has already said the cause was the incorrect installation of sensors detecting speed and direction.

Roscosmos chief Vladimir Popovkin said that the first rocket launch would take up a foreign satellite.

"By the end of the year we will try to carry out four to five Proton launches following the accident," he said, quoted by RIA Novosti.

The Proton-M rocket is Russia's most popular for commercial satellite launches. The latest failure came after a string of botched unmanned launches in the last two years seriously tarnished the reputation of the country's space programme.

Russian Prime Minister Dmitry Medvedev last month issued an official reprimand to the space agency chief for failing to carry out his duties properly.

After the withdrawal of the US shuttle, Russia is now the sole nation capable of transporting humans to the International Space Station (ISS).