"In general, Croatia continues to respond in a timely and adequate manner to the OTP’s requests for assistance and provides access to witnesses and evidence as required," read the report which Brammertz submits to the U.N. every six months.

During the reporting period, the inter-agency Task Force established in October 2009 to locate or account for the missing military documents concerning Operation Storm requested for the case of Croatian general Ante Gotovina and others, continued its administrative investigation, Brammertz said.

"Since December 2010, the Task Force submitted three reports (dated 18 January 2011, 4 February 2011, and 28 February 2011 respectively) and a separate report on 14 April 2011 summarising all of its activities and findings to date," the ICTY chief prosecutor said.

"A number of inconsistencies and questions raised in connection with the Task Force’s findings, as mentioned in the Prosecutor’s last Completion Strategy Report, remain unresolved. The missing documents are unaccounted for," Brammertz said in the report which he will present orally at the U.N. Security Council session in 6 June.

The chief prosecutor said that on 15 April 2011, the Trial Chamber rendered its judgement in the trial of Gotovina, Ivan Cermak and Mladen Markac, sentencing Gotovina to 24 years in prison and Markac to 18 years in prison for war crimes committed during and in the wake of Operation Storm. The Hague tribunal acquitted the third Croatian general in this case, Ivan Cermak.

During his visit to Croatia on 4 May 2011, the chief prosecutor was informed by the Croatian authorities that the Task Force will continue its administrative investigation into the missing documents originally requested by the OTP as well as for other documents required in national proceedings.

Full cooperation with the ICTY is one of the benchmarks for the closure of the policy area No. 23 the Judiciary and Fundamental Rights in Croatia's EU entry talks.

In his last report, submitted in December 2010, Brammertz described Croatia's cooperation with his office as generally positive, calling on Croatia to continue to solve problems and entirely shed lights in the disappearance of the wanted military documents referring the Operation Storm.

ICTY President Patrick Robinson in his report to the U.N. Security Council, in chapter entitled Cooperation of States, said that "it again must be reported that Ratko Mladic and Goran Hadzic continue to remain at large."

"It is noted, however, that there is general agreement amongst members of the Security Council that there will be no impunity regardless of when these remaining fugitives are apprehended. All States, especially those of the former Yugoslavia, are asked to intensify their efforts and to deliver these fugitives to the Tribunal as a matter of urgency," Robinson said.

Brammertz said the OTP was deeply concerned with Serbia's failure to locate and arrest the two remaining ICTY fugitives.