Sweden has in secret been helping Saudi Arabia plan the construction of an arms factory to produce anti-tank missiles, public broadcaster Swedish Radio reported Tuesday.

The Swedish Defense Research Agency (FOI) has helped Saudi Arabia since 2007, though construction on "Project Simoom" has yet to begin, the radio said citing hundreds of classified documents and interviews with key players.

Sweden has in the past sold weapons to Saudi Arabia, but classified government documents state that Project Simoom "pushes the boundaries of what is possible for a Swedish authority," the radio said.

"The fact that an authority such as FOI is involved in the planning of a weapons factory for a government in a dictatorship such as Saudi Arabia is quite unique," the radio said.

FOI director general Jan-Olof Lind denied the existence of the project.

"We do not have a project agreement with that country," he told the radio.

Asked specifically if there has been a Project Simoom with Saudi Arabia, Lind replied: "No. And I do not wish to comment on discussions that may or may not have occurred between Sweden and Saudi Arabia. These discussions are classified."

But several former FOI employees confirmed the existence of the project to Swedish Radio, including Dick Straeng who led the project until 2010 and was one of Lind's closest colleagues.