By Phil Mercer BBC correspondent in Sydney

A German tourist has been killed by a crocodile in Australia.

Northern Territory police say the 24-year-old woman was attacked at a waterhole in the Kakadu National Park during a midnight swim.

The woman was taking a midnight dip despite warning signs

Investigators believe the woman, who was on an organised tour, ignored signs warning of the danger from saltwater crocodiles.

Members of the touring party say they saw a dark shape emerge from the water and grab the woman before swimming away.

It is believed the victim's sister was beside her at the time.

The waterhole is understood to be clearly signposted, with warnings about crocodiles.

National park rangers have found the woman's body, and a four-metre crocodile suspected of killing her has been harpooned.

Police say it is still not clear why the group was swimming in an area infested with saltwater crocodiles.

The world's largest reptiles are aggressive and dangerous and can travel at great speeds through the water.

It is estimated around 100,000 live in tropical northern Australia.

They are protected and are believed to have killed more than a dozen people in the last 20 years.