Attribute "target_branch" is not working to get the merged items on particular branch

I am using GitLab version 10.3.5.

When i trying to get the merged items on a development branch(target_branch) alone between the dates using the GitLab API, it collects all the merged items on all target branches.

https://docs.gitlab.com/ee/api/merge_requests.html#list-merge-requests

Also, updated_after attribute not working.

How to resolve this?