DAKAR (Reuters) - Two Red Cross workers were killed on Wednesday when their car was attacked by unidentified armed men in western Mali, the global humanitarian organisation said on Thursday.

       Armed men on motorcycles opened fire on the vehicle in the region of Kayes, the Malian Red Cross said in a statement.

       The driver, who was Malian, and a staff member of the Netherlands Red Cross were killed, it said, while two colleagues survived the attack.

       The area where the team was driving was considered relatively safe, the International Red Cross and Red Crescent Movement said in a separate statement, although large swathes of the West African country are overrun by Islamist militants.

       "The International Red Cross and Red Crescent Movement is deeply concerned about the worsening security situation in the Sahel region," the statement said. "This violence, and the specific targeting of humanitarian workers, makes it hard for Red Cross teams to provide the needed assistance to vulnerable communities in the region."

       An Islamist insurgency that started in Mali a decade ago has since spread to neighbouring Niger and Burkina Faso. Some of the groups fighting have links to al Qaeda and Islamic State.

       (Reporting by Nellie Peyton; Editing by Leslie Adler)