Ant build failed: "Target "build..xml" does not exist"

When I run the ant file in verbose mode, I got an error like the one below. Does anyone have any ideas what is going wrong? I am new to this

antlib:org.apache.tools.ant] Could not load definitions from resource org/apach
e/tools/ant/antlib.xml. It could not be found.
Override ignored for property "java.home"
BUILD FAILED
Target "build.xml" does not exist in the project "MYPROJECT".
        at org.apache.tools.ant.Project.tsort(Project.java:1821)
        at org.apache.tools.ant.Project..topoSort(Project.java:1729)
        at org.apache.tools.ant.Project.topoSort(Project.java:1692)
        at org.apache.tools.ant.Project.executeTarget(Project.java:1298)
        at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
        at org.apache.tools.ant.Project.executeTargets(Project.java:1181)
        at org.apache.tools.ant.Main.runBuild(Main.java:698)
        at org.apache.tools.ant.Main.startAnt(Main.java:199)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:257)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:104)
Total time: 1 second

This is my build.xml:

<project name="MYPROJECT" default="dev" basedir=".">
  <property name="build.home" value="build/jsp" />
  <property name="tomcat.home" location="../Tomcat 5.0/" />
  <path id="project.class.path">
    <fileset dir="./lib/">
      <include name="**/*.jar" />
    </fileset>
  </path>
  <target name="reltag">
    <tstamp>
      <format property="now" pattern="d MMM yyyy HH:mm" />
    </tstamp>
    <property name="reltag" value="Built date: ${now}" />
  </target>
  <target name="dev" depends="compile" description="Builds for development">
    <mkdir dir="jsp/WEB-INF/lib" />
    <mkdir dir="jsp/WEB-INF/classes" />
    <copy todir="jsp/WEB-INF/lib">
      <fileset dir="lib">