Members of the America's Cup team Alinghi say they have received threats against themselves and their families.

Alinghi officials say they have been sent two letters from so-called "patriotic activists" threatening New Zealanders involved with the Swiss syndicate.

New Zealand police said the letters, from a group calling itself Teach the Traitors A Lesson (TTAL), indicated an intention to target the children and family of the team's Kiwi sailors.

Star skipper Russell Coutts defected to Alinghi from New Zealand's America's Cup-winning team in 2000.

He took several other New Zealanders with him, including tactician Brad Butterworth.

We came here, in New Zealand, to sail, not to have our children threatened Alinghi official Michael Bonnefous

Alinghi executive director Michael Bonnefous alleged the letters promised to damage team members' property and inflict violence on their families.

They said they had tracked the movements of children and other family members, and gave personal details about one crew member.

"I am horrified by the tone in these letters, as I am sure most New Zealanders will be," said Bonnefous.

"Alinghi is an international team. We are open and want to share our passion for sailing.

"We want the focus to return to sport and to the action on the water. We came here, in New Zealand, to sail, not to have our children threatened."

It's being treated extraordinarily seriously Jeoff Barraclough, New Zealand police

Police investigations have been underway since the two letters were received in mid-December, according to a police spokesman.

"At the moment the letters are undergoing forensic testing," said America's Cup police spokesman Jeoff Barraclough.

"This is a threat, and its a threat to harm. So it's being treated extraordinarily seriously."

But Barraclough denied that BlackHeart, a group campaigning against Kiwis competing for other Cup syndicates, was responsible for the threats.

And BlackHeart spokesman David Walden said: "BlackHeart neither has sent nor will send any threatening letters to the members of rival syndicates or their families.

"We are fully cooperating with the police in their efforts to find the people who did."

Alinghi will meet Oracle in the final of the Louis Vuitton Cup, which starts on 11 January.

The winners will take on Team New Zealand for the America's Cup in February.