KYIV, Oct 27 (Reuters) - The heads of Ukraine"s national anti-doping organisation (NADC) resigned on Wednesday after being accused of violating international standards, the Ukrainian sports minister said. The World Anti-Doping Agency (WADA) this week said it had evidence that the Ukrainian agency had violated doping sample collection rules by effectively warning athletes in advance of future tests. "NADC has violated the international testing standard. Today, the director of NADC Ivan Kurlishchuk and his deputy Yaroslav Kruchek resigned," Vadym Huttsait said in a statement. "The ministry states that we take a clear position in the fight against doping and will not allow anyone to violate anti-doping rules," he added. The NADC was not immediately available for comment.