Sri Lankan President Mahinda Rajapaksa. Pic: AP.

COLOMBO, Sri Lanka (AP) — A Sri Lankan activist says President Mahinda Rajapaksa’s decision to deny entry to U.N. investigators is intended to undermine the credibility of an ongoing war crimes inquiry.

Paikiyasothy Saravanamuttu, chief of independent think tank Center for Policy Alternatives, said Thursday he believes the inquiry could still be conducted effectively because much evidence is available outside Sri Lanka.

Rajapaksa said Tuesday that he will not allow the three U.N. panelists to visit Sri Lanka to inquire into allegations of war crimes against the government troops and now-defeated Tamil Tiger rebels at the end of the civil war in 2009.

A previous U.N. report said up to 40,000 ethnic Tamil civilians may have been killed in just the last month of the fighting.