national characters are not loaded correctly from Apache Ant XML file

I have the following Apache Ant test file:

<?xml version="1.0" encoding="UTF-8"?>
<project name="test">
<property name="str" value="this is a test, ěščřžýáíéůú" />
<target name="test">
    <echo message="str is &quot;${str}&quot;" />
</target>
</project>

As you can see, the property contains some national characters. The national characters do not seem to be loaded correctly from the Apache Ant XML file. It shows only question marks ? in both console and output file produced by -l switch. I have tested with Apache Ant(TM) version 1.9.1 compiled on May 15 2013.

What can I do about it?