Pakistan allowed Chinese military engineers to photograph and take samples from the top secret stealth helicopter that U.S. special forces left behind when they killed Osama bin Laden, the Financial Times has learnt.

A crashed military helicopter is seen near the hideout of Al-Qaeda leader Osama bin Laden after a ground operation by US Special Forces in Abbottabad on May 2, 2011. Pakistan said that the killing of Osama bin Laden in a US operation was a "major setback" for terrorist organisations and a "major victory" in the country's fight against militancy.

The action is the latest incident to underscore the increasingly complicated relationship and lack of trust between Islamabad and Washington following the raid.