Can't ssh into cloud shell

Question

I try to ssh from my local host to GCP cloud shell and get the error:

$ gcloud cloud-shell ssh --authorize-session sign_and_send_pubkey: signing failed for RSA "/home/kossak/.ssh/google_compute_engine" from agent: agent refused operation <USER>@<IP>: Permission denied (publickey). ERROR: (gcloud.cloud-shell.ssh) [/usr/bin/ssh] exited with return code [255]. 

with debug option:

$ gcloud cloud-shell ssh --authorize-session --verbosity debug DEBUG: Running [gcloud.cloud-shell.ssh] with arguments: [--authorize-session: "True", --verbosity: "debug"] DEBUG: Starting new HTTPS connection (1): cloudshell.googleapis.com:443 DEBUG: https://cloudshell.googleapis.com:443 "GET /v1/users/me/environments/default?alt=json HTTP/1.1" 200 None DEBUG: Starting new HTTPS connection (1): cloudshell.googleapis.com:443 DEBUG: https://cloudshell.googleapis.com:443 "POST /v1/users/me/environments/default:authorize?alt=json HTTP/1.1" 200 None DEBUG: Running command [/usr/bin/ssh -t -p 6000 -i /home/kossak/.ssh/google_compute_engine -o StrictHostKeyChecking=no <USER>@<IP> -- DEVSHELL_PROJECT_ID=<PROJECT_ID> bash -l]. DEBUG: Executing command: ['/usr/bin/ssh', '-t', '-p', '6000', '-i', '/home/kossak/.ssh/google_compute_engine', '-o', 'StrictHostKeyChecking=no', '<USER>@<IP>', '--', 'DEVSHELL_PROJECT_ID=<PROJECT_ID>', 'bash -l'] sign_and_send_pubkey: signing failed for RSA "/home/kossak/.ssh/google_compute_engine" from agent: agent refused operation <USER>@<IP>: Permission denied (publickey). DEBUG: (gcloud.cloud-shell.ssh) [/usr/bin/ssh] exited with return code [255]. Traceback (most recent call last): File "/home/kossak/apps/google-cloud-sdk/lib/googlecloudsdk/calliope/cli.py", line 987, in Execute resources = calliope_command.Run(cli=self, args=args) File "/home/kossak/apps/google-cloud-sdk/lib/googlecloudsdk/calliope/backend.py", line 807, in Run resources = command_instance.Run(args) File "/home/kossak/apps/google-cloud-sdk/lib/surface/cloud_shell/ssh.py", line 114, in Run command.Run(connection_info.ssh_env) File "/home/kossak/apps/google-cloud-sdk/lib/googlecloudsdk/command_lib/util/ssh/ssh.py", line 1541, in Run raise CommandError(args[0], return_code=status) googlecloudsdk.command_lib.util.ssh.ssh.CommandError: [/usr/bin/ssh] exited with return code [255]. ERROR: (gcloud.cloud-shell.ssh) [/usr/bin/ssh] exited with return code [255]. 

What I tried already:

• restarting ssh-agent on local machine
• rebooting my local machine and cloud shell
• gcloud compute config-ssh (on both local machine and cloud shell) returned only WARNING: No host aliases were added to your SSH configs because instances have no public IP.
• removing all ssh keys from GCP Compute => Metadata => SSH Keys
• renaming ~/.ssh and trying to connect again
• ssh-add -l returns both of my keys: rsa (from gcp) and ed25519 (created manually)
• permissions of /home/kossak/.ssh are 700
• permissions of /home/kossak/.ssh/google_compute_engine are 600
• connecting to another SSH server in my local network with a ssh key - works properly
• executing git commands with ssh key authorization (eg git remote update) - works properly

I use:

• Linux Manjaro
• Google Cloud SDK 410.0.0

I can login to cloud shell from another host so the problem is probably with my computer. Anybody knows what's wrong or how to debug it?

Thank you for any advice.