SAN FRANCISCO (Reuters) - Amazon.com Inc shares were downgraded by Morgan Stanley analysts on Thursday on concern about competition from Apple Inc and slowing sales growth.

Analysts led by Scott Devitt lowered their rating on Amazon shares to "equal weight" from "overweight." Amazon's shares fell 4.1 percent to $176.97 in morning trading.

(Reporting By Alistair Barr; Editing by Maureen Bavdek)