Somaliland's people have voted overwhelmingly to support a new constitution confirming independence from the rest of Somalia, according to early returns from a referendum held on Thursday.

"So far more than 80 percent of the votes counted are 'Yes'," referendum official Khalil Ibrabhim Hawadleh told Reuters. Hawadleh, who is also deputy mayor of the capital Hargeisa, was referring to votes from the territory's most heavily populated region -- Hargeisa and its surrounding areas.

Most religious and clan leaders urged people to endorse the new constitution in Thursday's polling, which gave voters the choice of backing or rejecting a new constitution that cements independence from Somalia.

Somaliland, a former British protectorate, split unilaterally from Somalia 10 years ago after a long independence struggle, taking advantage of the chaos that followed the fall of Somali dictator Mohamed Siad Barre.

In the years that followed, much of the rest of Somalia descended into clan-based anarchy, while the people of Somaliland rebuilt their country in peace.

Yet Somaliland's independence has never been recognised by the international community, something which rankles with many ordinary people and with the government.

Preliminary results for the whole territory are expected to be announced later on Saturday, said Abdulqadir Jirde, deputy chairman of the central commission of the referendum. The polling was monitored by observers from the United States and South Africa.

The referendum is aimed in part at advancing Somaliland's international campaign for recognition by demonstrating popular support for an independence constitution.

But the referendum has encountered some opposition, especially from outside the territory.

Last year, clan leaders from all over Somalia elected a new transitional national government and a president, Abdiqassim Salad Hassan, after a lengthy meeting in neighbouring Djibouti.

Abdiqassim's government, which sits in the Somali capital Mogadishu, is fiercely opposed to the idea of a referendum in Somaliland, which it claims as part of Somalia. Hargeisa is a city of 110,000, but reliable figures for Somaliland's population as a whole are not available due to the nomadic lifestyle of local clans.

Somalia, including Somaliland, is estimated to have a population of between eight million and nine million.