Botswana President Ian Khama's ruling party yesterday held a firm lead in parliamentary poll results in the diamond-rich nation's toughest election since independence four decades ago.

With 19 out of the 21 seats declared so far, the Botswana Democratic Party was only 10 seats away from being able to claim victory.

The main opposition Botswana National Front had only one seat, overtaken by its offshoot, the Botswana Congress Party, which had secured three seats.

But despite an overall lead, officials expressed regret at being unable to win all the seats.

"We are not happy. We have lost key constituencies which were previously ours," said BDP election committee member Langston Motsete who added that the party had been "massacred" in Gaborone central, which it also lost in the last poll in 2004.

In many cases there were only a handful of votes between the winner and runner-up. The country operates a first-past-the-post electoral system.

An observer mission from the Southern African Development Community (SADC) bloc said vote counting was proceeding slowly, but that polls had been peaceful and calm with no reports of intimidation.

"It was a peaceful way of voting... everything was really calm," said Henrique Banze, deputy foreign minister of Mozambique and leader of the 88 SADC observers.

"It is a little bit in our view, slow, but I do understand all the procedures meant to give as much transparency as possible."

Africa's flagship democracy Botswana is often hailed for its stability in an often volatile continent, in sharp contrast to neighbouring Zimbabwe where failed elections last year were accompanied by violence and economic crisis.

This year's polls in Botswana have been the toughest yet with bitter infighting in the ruling party, which has ruled since independence in 1966, and an economy hard hit by falling diamond revenues. The country is the world's biggest diamond producer. The BDP was expected to remain in charge with little contest from a weak opposition, after overseeing four decades of stability, despite growing unease over Khama's leadership style, said to be authoritarian and non-consultative.

The tough-talking Khama is popular abroad, having often broken ranks with regional leader's softly-softly approach to criticise democratic abuses by Zimbabwe's President Robert Mugabe.