Image caption Poaching and deforestation have caused a sharp decline in the tiger population

The number of wild tigers living in Nepal has increased by 63% to 198 since 2009, a government survey has shown.

The survey, which was carried out between February and June, assessed the Bengal tiger population across a 600-mile stretch in Nepal and India.

It found numbers had increased in all of Nepal's national parks.

South Asian governments have committed to doubling tiger populations by 2022, but the animals continue to face threats from poaching and habitat loss.

There are thought to be fewer than 2,000 tigers left worldwide, with 60% of them in India.

The survey covered tigers in the Terai Arc region, which spreads across the north Indian states of Bihar, Uttar Pradesh and Uttarakhand and into southern Nepal.

'A milestone'

Nepal's survey concentrated on five protected areas and three wildlife corridors.

The results show the number of tigers in Nepal have increased to 198, a rise from 121 in 2009.

In particular, the tiger population in the south-western Bardia national park has risen from about 18 in 2009 to 50 this year.

Nepalese officials described the findings as a "milestone" in the bid to double the number of wild tigers by 2022, as agreed by the region's leaders at an international summit in 2010.

Image caption Wild tigers were assessed in the Terai Arch region

"Tigers are a part of Nepal's natural wealth and we are committed to ensuring these magnificent wild cats have the prey, protection and space to thrive," the director-general of Nepal's Department of National Parks and Wildlife Conservation, Megh Bahadur Pandey, said.

Tens of thousands of Royal Bengal tigers, the most numerous subspecies of tiger, used to roam Bangladesh, Bhutan, India and Nepal, but their numbers have fallen dramatically in recent decades.

The tiger's massive decline is due to widespread deforestation, the shrinking of their habitat and loss of prey base, as well as illegal poaching and wildlife trade.

Earlier this year, a study by Cardiff University warned that Indian tigers could face extinction because of a collapse in the variety of their mating partners.

The study found that 93% of DNA variants found in tigers shot during the period of the British Raj are not present in tigers today.

Researchers say a loss of habitat has meant that tigers are no longer free to roam throughout the subcontinent, which in turn has restricted their gene pool.

In Nepal, officials have increased anti-poaching efforts in a bid to curb the illegal wildlife trade, aimed at strengthening protection for the species.