The vote is controversial both inside and outside Somaliland.

But Somaliland's leader, President Mohamed Ibrahim Egal, is determined that what he terms a successful new state is allowed to disassociate itself from war-torn Somalia.

Hurdles

The referendum will determine whether independence is supported by the majority of people in Somaliland, but it remains to be seen whether the result will be endorsed by the international community.

Voters were queuing up when the 600 polling stations opened at 0600 local time (0300 GMT), the news agency AFP said.

The vice-chairman of the national constitutional commission said he was hoping for a turnout of 60%.

But the vote is not straight forward:

• There is no census, so community elders are deciding who should vote
• In two areas local people are divided over whether they should belong to Somaliland or the neighbouring administrative region of Puntland
• Some in Somaliland do not want to break from Somalia at all

The Organisation of African Unity (OAU) and the United Nations also refuse to lend their support, declaring that they fully support Somalia's new administration, even though its control barely extends beyond a few areas of the capital Mogadishu.

Stability

But the BBC Africa Analyst says that Somaliland has achieved a level of stability not seen in the rest of Somalia.

While Mogadishu is terrorised by competing armed factions, Somaliland's capital Hargeisa is one of the safest cities on the continent.

The international community's reluctance to endorse Somaliland's independence is based on the principle - enshrined in the OAU charter - of the inviolability of colonial borders.

Unofficially, "everybody is afraid of a proliferation of mini-states" which would be unsustainable and could lead to endless border disputes, said one Somalia expert quoted by AFP.

Historically distinct

Somaliland has been officially independent before - for four days in 1960, between the end of British colonial rule and integration with the rest of Somalia which had been under Italian administration.

To the rest of the world, Somaliland remains an invisible state.

In London on Thursday a crowd of supporters demonstrated near the British prime minister's official residence, calling on Somaliland's former colonial power to be the first to recognise the state's independence.