#tallships – Rescue officials say they have "grave concerns" for seven people aboard a US schooner that has been missing for three weeks between New Zealand and Australia.

Authorities said the Nina, an 84-year-old wooden vessel, is skippered by American David Dyche.

There are two other American men and three American women aboard, aged between 17 and 73, and a 35-year-old British man.

Maritime New Zealand said extensive searches by plane this week had found no sign of the 21m (70ft) schooner.

It set off from the Bay of Islands settlement of Opua on New Zealand's North Island on May 29 bound for the Australian city of Newcastle, north of Sydney.

A New Zealand meteorologist took the last known calls from the crew on board the yacht when it was about 370 nautical miles west of New Zealand.

"The weather's turned nasty, how do we get away from it?" Bob McDavitt was asked when he took a satellite phone call from Nina on June 3.

A storm around at the time saw winds gusting up to 110km/h (68mph) and waves of up to 8m (26ft).