External IDP not Logged Out

Keycloak standard logout fails to logout from external identity provider.

We have configured a Java based application secured by Keycloak and setup an external IDP(OIDC). When logging out of the application, the Keycloak session is terminated; however, the external IDP remains logged in. The user is able to access the application even after logging out of Keycloak session in browser.

Attached IDP configuration settings for reference.

Suggestions would be much appreciated.