A Moscow radio announcer who altered official news bulletins to portray Soviet forces in Afghanistan as ''invaders'' has been returned to work in broadcasting after psychiatric treatment, a senior Soviet radio official said today.

He said that the announcer, Vladimir Danchev, 35 years old, was again working for the State Committee for Television and Radio Broadcasting. The official said he was ''not sure'' of the job assigned to Mr. Danchev.

''He is back at work, but he will not necessarily be involved with the English-language service,'' the official said, referring to the section for which the announcer had worked.

Mr. Danchev was suspended after he had read a series of news bulletins over the English service in which key passages had been altered to reverse the usual Soviet position.