Photo: AFP

Some 600 people have been invited to the wedding of Britain's Prince Harry and his fiancée Meghan Markle, Kensington Palace announced on Thursday.

The invitations were posted earlier this week, Harry's official residence said - without revealing who had made the guest list.

Harry and his US actress fiancée are set to tie the knot at Windsor Castle, west of London, on May 19.

The 600 invitees will attend the service in the castle's St George's Chapel, followed by the lunchtime reception hosted by Harry's grandmother Queen Elizabeth II at St George's Hall.

Prince Harry, Meghan Markle's royal wedding invitations. Photo: AFP

Later, around 200 guests are being invited to a private reception at Frogmore House given by Harry's father Prince Charles, the heir to the throne.

The venue for the evening party, in the park outside Windsor Castle, is where Harry and Markle posed for their official engagement photos.

The invitations, issued in Charles's name, were on thick white card gilded along the edge, which were die-stamped in gold and then burnished.

The invitations read: "His Royal Highness The Prince of Wales ... requests the pleasure of the company of ... at the marriage of His Royal Highness Prince Henry of Wales with Meghan Markle at St George's Chapel, Windsor Castle on Saturday 19th May, 2018 at 12 Noon followed by a reception at Windsor Castle."

The names of the invited guests were added in later by a calligraphy printer.

Uniforms and elderflower cake

The invites indicated that the dress code is uniform, morning coat or lounge suit, or day dress with a hat.

Harry, a former soldier who also holds ceremonial military roles, is therefore likely to be wearing his highest-ranking uniform for the wedding.

The prince and his bride-to-be have been increasingly busy this month in the build-up to the big day.

On Tuesday, the couple announced they had chosen London-based US pastry chef Claire Ptak to make a lemon elderflower wedding cake, to be covered with buttercream and decorated with flowers.

Queen Elizabeth published her formal consent to the marriage on Mar 15.

By law, the monarch must give consent for the marriage of the first six people in line to inherit the throne.

Harry, 33, is fifth in line after his father Charles, brother Prince William and William's children Prince George and Princess Charlotte.

He will be bumped down to sixth place when William's wife Kate gives birth next month.

On Mar 12, Markle took part in her first official event with Queen Elizabeth, accompanying Harry to a Commonwealth Day service at London's Westminster Abbey.

Markle, 36, was baptised by the leader of the Church of England earlier this month out of respect for the sovereign's role as head of the denomination.