The family of a missing German tourist who's been cycling the North Island are asking Kiwis to keep an eye out.

Alexander Gaitzsch's family say they haven't heard from the 24-year-old in two weeks.

His godmother Babett Bildergalerie says he's usually in touch every two or three days - and he missed his mother's birthday.

She says he's 1.7m tall with an athletic build and dark blond hair - and should be riding a black Winora bike.

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Bildergalerie says people have reported potential sightings from Whangarei to Kāpiti Coast.

More than 8000 people have shared her appeal on social media - and have been checking in with ferry companies and local campgrounds.

Police say they haven't received a report - but are making inquiries.