The World Anti-Doping Agency (WADA) described itself as "very disturbed" by a documentary alleging suspected doping in international athletics.

A documentary, titled 'Doping – Top Secret: The Shadowy World of Athletics', was released by German broadcaster ARD on Saturday.

The broadcaster and The Sunday Times claim to have obtained a leaked database belonging to the IAAF containing 12,000 blood tests from around 5,000 athletes in the years 2001 to 2012.

The Times says the evidence reveals the "extraordinary extent of cheating" by athletes at big events.

In a statement, WADA president Sir Craig Reedie said: "WADA is very disturbed by these new allegations that have been raised by ARD; which will, once again, shake the foundation of clean athletes worldwide.

"Given the nature of these allegations, which are an extension to those that were raised by ARD’s December 2014 documentary, they will immediately be handed over to WADA’s Independent Commission for further investigation.

"These allegations require swift and close scrutiny to determine whether there have in fact been breaches under the World Anti-Doping Code and, if so, what actions are required to be taken by WADA and/or other bodies.

"As always, WADA is committed to doing what’s necessary to ensure a level playing field for clean athletes of the world."

The documentary, released late last year, led to the formation of an Independent Commission which is scheduled to deliver its report into allegations of doping practices, among other matters, by the end of the year.