Releasing a multi-module maven project with Git

I'm trying to release a multi-module maven project that uses git as the SCM, and among the first problems I've encountered is the way in which the maven release plugin builds the release.properties scm.url. My parent POM looks something like this:

<packaging>pom</packaging>
<groupId>org.project</groupId>
<artifactId>project-parent</artifactId>
<version>1.0.0-SNAPSHOT</version>

<scm>
    <connection>scm:git:git://github.com/username/project.git</connection>
    <developerConnection>scm:git:git@github.com:username/project.git</developerConnection>
    <url>http://github.com/username/project</url>
</scm>

<modules>
    <module>api</module>
    <module>spi</module>
</modules>

And the module POMs are straightforward:

<parent>
    <groupId>org.project</groupId>
    <artifactId>project-parent</artifactId>
    <version>1.0.0-SNAPSHOT</version>
</parent>
<artifactId>api</artifactId>
<version>0.2.2</version>

My goal is to be able to release individual modules since they each have different versions and I don't want to increment all of the versions together each time I do a release.

When I change to the api directory and do a mvn release:clean release:prepare I'm met with the following output:

[INFO] Executing: cmd.exe /X /C "git push git@github.com:username/project.git/api master:master"
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Unable to commit files
Provider message:
The git-push command failed.
Command output:
ERROR: Repository not fo