How to disable index in innodb

I'm trying to speed up bulk insert in an InnoDB table by temporary disabling its indexes:

ALTER TABLE mytable DISABLE KEYS;

But it gives a warning:

+-------+------+-------------------------------------------------------------+
| Level | Code | Message                                                     |
+-------+------+-------------------------------------------------------------+
| Note  | 1031 | Table storage engine for 'mytable' doesn't have this option |
+-------+------+-------------------------------------------------------------+
1 row in set (0.00 sec)

How can we disable the indexes?

What alternatives are there to avoid using the index when doing bulk inserts?

How can we speed up the process?