( CNN ) -- A Mali separatist movement on Sunday said it was prepared to act against Islamic militants following the destruction of three sacred tombs in Timbuktu , and called on the United States and France `` to help us kill them . '' The tombs , a 15th-century shrine to Muslim saints , are part of a UNESCO World Heritage site in Timbuktu . UNESCO on Saturday condemned the destruction and called for it to stop . The U.N. agency , which sponsors cultural , scientific and educational programs to further peaceful relations between nations , has received reports that three of the site 's 16 mausoleums were `` completely destroyed , '' UNESCO Director General Irina Bokova told CNN on Sunday . They are the mausoleums of Sidi Mahmoud , Sidi Moctar and Alpha Moya . Islamic militants set fire to sacred tombs in Timbuktu . Timbuktu Mayor Ousmane Halle said that Muslims on their way to Friday worship at the tombs were stopped and threatened by armed men from Ansar Dine , a militant group that seeks to impose strict Sharia law . Ansar Dine has threatened to continue the destruction . `` It 's very , very bad for the Azawad people and the whole world what Ansar Dine has done in Timbuktu . We condemn it completely , '' Moussa Ag Assarid , spokesman for the Tuareg rebels ' National Movement for the Liberation of Azawad , or MNLA , said Sunday . The group promotes a separate state it calls Azawad . `` We are ready and preparing to right with these terrorist organizations , '' Assarid said . `` We will move soon , and ( are ) taking our arms and vehicles and material , but we still need help . '' The MNLA claims Islamist extremist groups including Ansar Dine , Boko Haram and al Qaeda have seized control of Timbuktu along with the towns of Gao and Kidal , and have killed top MNLA leaders there . `` We call on the USA , France and all other countries who want to stand against Ansar Dine , Boko Haram and al Qaeda who are now holding Timbuktu , Gao and Kidal to help us kill them and help the people in those cities , '' Assarid said . U.N. Secretary-General Ban Ki-moon is `` concerned by the worsening security and humanitarian situation in northern Mali '' and reports of the destruction , his office said in a statement . `` Such attacks against cultural heritage sites are totally unjustified , '' the statement said . Witnesses said the destruction began on Friday . `` The militants broke the doors and wooden gates to the grave and then used the cloth inside to set fire to the tomb , '' said Sankoum Sissoko of Timbuktu . `` They started chasing people away , telling them they should n't worship a saint , a human being . '' The World Heritage Committee on Thursday accepted the request of Mali 's government to place Timbuktu on the list of endangered UNESCO sites . That request was reportedly what angered the militants , who accused UNESCO of cooperating with the government . Timbuktu 's treasures at risk . France , the former colonial power in Mali , also condemned the attack , calling for an end to the violence . Mali was plunged into chaos by a military coup in March that ousted former President Amadou Toumani Toure . Since then , the Tuareg rebels and the Islamists have taken advantage of the uncertainty to attempt to seize control over the northern portion of the nation . Rebels burn Timbuktu tomb . CNN 's Brian Walker contributed to this report .
Tuareg rebels say they want the United States and France to help . Three tombs at a UNESCO World Heritage site in Timbuktu are reported destroyed . The U.S. State Department says it is aware of reports that some American citizens have been kidnapped by militants linked to al Qaeda in northern Mali.