Error "Source option 5 is no longer supported. Use 6 or later" on Maven compile

I am getting the following error or $ mvn compile:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project Sym360: Compilation failure: Compilation failure: 
[ERROR] Source option 5 is no longer supported. Use 6 or later.
[ERROR] Target option 1.5 is no longer supported. Use 1.6 or later.
[ERROR] -> [Help 1]

Here is the code of my pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
 http://maven.apache.org/maven-v4_0_0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <groupId>com.test.app</groupId>
 <artifactId>Tset</artifactId>
 <packaging>jar</packaging>
 <version>1.0-SNAPSHOT</version>
 <name>Test</name>
 <url>http://maven.apache.org</url>

 <properties>
   <maven.compiler.source>6</maven.compiler.source>
   <maven.compiler.target>1.6</maven.compiler.target>
 </properties>

<build>
<pluginManagement>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.22.1</version>
    </plugin>
  </plugins>
</pluginManagement>
</build>
<dependencies>

<!-https://mvnrepository.com/artifact/org.seleniumhq.selenium/selenium- 
java -->
<dependency>
    <groupId>org.seleniumhq.selenium</groupId>
    <artifactId>selenium-java</artifactId>
    <version>3.14.0</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.testng/testng -->
<dependency>
    <groupId>org.testng</groupId>
    <artifactId>testng</artifactId>
    <version>6.14.3</version>
    <scope>test</scope>
</dependency>

I tried to add properties in the pom.xml code, but still getting the same error. Can someone help me in resolving this issue? Thanks in advance