Beyonce and Jay-Z have reportedly sought trademark protection for the names of their twins before announcing publicly what they are called.

The company that owns trademarks to the performers' own names filed legal documents for "Rumi Carter" and "Sir Carter" a week ago.

It followed the birth of the twins in mid-June and came as the names have still to be announced.

Trademark protections were sought for items including fragrances, cosmetics, key chains, baby teething rings, strollers, mugs, water bottles, hair ribbons and rattles, the showbusiness website TMZ reported.

Others included books, flags, sports gear, clothing, musical performances and entertainment services.

It was not confirmed that the children were called "Rumi" and "Sir" but the couple used the same company when they registered "Blue Ivy" as a trademark in 2012, which was later confirmed as the name of their first daughter.