docker-compose creating multiple instances for the same image

I need to start multiple containers for the same image. If i create my compose file as shown below, it works fine.

version: '2'

services:
  app01:
    image: app
  app02:
    image: app
  app03:
    image: app
  app04:
    image: app
  app05:
    image: app  

Is there any easy way for me to mention the number of instances for the compose instead of copy and pasting multiple times?

Updated answer (Oct 2017)

As others mentioned, the docker API has changed. I'm updating my answer since it's the one most people will probably look at.

docker-compose up -d --scale app=5

Unfortunately, we cannot specify this in a docker-compose.yml file currently (as of version 3.5).

Details:
They did introduce the scale option for version 2.2 and 2.3 of docker-compose but removed it for version 3.0. Also, to use version 2.2 or 2.3 you would need to download an older version of the docker-compose tool. The current version does not support 2.2 or 2.3 (it does support 2.0 or 2.1 however). There is also a new deploy section with replicas: 5 but it's only for swarm mode.

--- Old Answer --------------------------------------

docker-compose scale app=5

See https://docs.docker.com/compose/reference/scale/

Then you only need this docker-compose file

version: '2'

services:
  app:
    image: app

You can do it with replica as mentioned in https://docs.docker.com/compose/compose-file/#replicas

version: '3'
services:
  worker:
    image: dockersamples/examplevotingapp_worker
    networks:
      - frontend
      - backend
    deploy:
      mode: replicated
      replicas: 6

Edit (from the comments): One can use docker-compose --compatibility up to make docker accept deploy section without using swarm.

The scale command is now deprecated, you should use up instead.

docker-compose up --scale app=2

more details in https://docs.docker.com/compose/reference/up