South Africa coach Peter de Villiers praised his side after they returned home with their third Tri-Nations title and first since 2004 - and then sent out an ominous warning to the rest of the rugby world.

The Springboks made a triumphant return to the country on Monday after sealing the title with a 32-29 victory over New Zealand in Hamilton - their fifth win out of six in the competition. They also won a hard-fought series against the British and Irish Lions 2-1 earlier this year.

"We are number one in the world, but the most difficult part lies ahead - that is staying there," said de Villiers. "There is a lot of room for improvement and it's all relative being the best because a team will lose a game or two from time to time. However, this team has not yet reached its peak. That is the challenge - it's going to be wonderful to take it to the next level."