Why do Indians use "refer (object)" instead of "refer to (object)"?

I've noticed this being done by all my offshore Indian colleagues. They say and write things like, "Please refer attachment" or "Refer the documentation page", instead of "Please refer to the attachment" or "Refer to the page" etc.

Is there an explanation for that? And what do you call a verb that is used in conjunction with a preposition like this (listen to, think of, refer to)?

It is a confusion over how the verb is used. I'm a little fuzzy on the official terminology, but note, e.g., that if one substitutes "read" for "refer" then the simple example (sans "to") works OK.

While both "read" and "refer" are transitive verbs, the object of "refer" is the person or thing being directed (e.g., "Refer him to the director for more information"), while the object of "read" is the thing being read.

I suspect that the Indian verb that most closely corresponds to "refer", in the sense we're discussing, has as its object the thing being referred to rather than the person/thing being directed. Thus, when the English word is substituted the wrong structure is applied.