Australian authorities plan to round up about 6,000 wild camels with helicopters and shoot them after they overran an outback town in search of water, trampling fences, smashing tanks and contaminating supplies.

The Northern Territory government announced its plan yesterday for Docker River, a town of 350 residents where thirsty camels have been arriving every day for weeks because of drought conditions.

"The community of Docker River is under siege by 6,000 marauding, wild camels," the local government minister, Rob Knight, said in Alice Springs, 310 miles (500km) north-east of Docker. "This is a very critical situation out there, it's very unusual and it needs urgent action."

The camels, which are not native to Australia but were introduced in the 1840s, have butted water tanks, approached houses to try to take water from air conditioning units and knocked down fencing at the small airport runway, Knight said.

The carcasses of camels killed in stampedes at water storage areas were contaminating the water supply, he said.

The government plans to use helicopters next week to herd the camels about nine miles outside the town and shoot them, leaving their carcasses to rot in the desert. A grant of A$49,000 (£27,000) will be provided for the cull and to repair damaged infrastructure.

"We don't have the luxury of time because the herd is getting bigger," Knight said.

It is common to see some camels in the remote community, but the continuing drought and an early heatwave have dried up other water sources and forced more of them into the town. Much of Australia is gripped by some of the worst drought conditions on record.

In August, the federal government set aside A$19m for a programme to slash the wild camel population, including a possible mass slaughter.

Glenys Oogjes, executive director of the national advocacy group Animals Australia, said the plan to kill camels by helicopter was barbaric, and that the community could instead set up barriers to keep out the camels.

"It's a terrible thing that people react to these events by shooting," she said. "The real concern is the terrible distress and wounding when shot by helicopter ... There will be terrible suffering."

Explorers brought camels to Australia to help them travel in the desert, and now an estimated 1 million roam wild across the country. They compete with sheep and cattle for food, trample vegetation and invade remote settlements in search of water, scaring residents as they tear apart bathrooms and rip up water pipes.

Docker River residents were not especially concerned when about 30 camels came into the town looking for water a few weeks ago, said Graham Taylor, head of the local council. But fears grew as more animals arrived every day.

He said many people were too frightened to leave their homes because of the animals, which can grow up to 2.1 metres (7 ft) tall and weigh 900kg (2,000lb).

"We need to get the risk and that threat away from the people," he said.