BANGALORE, April 13 (Reuters) - Khan Resources Inc said Mongolia's Nuclear Energy Agency (NEA) invalidated the mining and exploration licenses of two of its units citing certain violations, sending its shares down 40 percent, their largest ever fall on a single day.

The Canadian explorer, which has been facing trouble from the Mongolian authorities with regard to its uranium projects in the country, said it intends to challenge the decision through all legally available means, including international arbitration.