Cocoa prices are continuing to rise as a result of the civil war in the Ivory Coast, the world's biggest cocoa bean producer, and exporters fear the trade could be paralysed.

The conflict in the West African state is coinciding with a surge in demand for cocoa around the world.

Prices for the bean have shot up from $1,444 a tonne in early June to $2,269 a tonne on Tuesday, the highest level for 16 years, as the potential for disruption grows.

The collapse of ceasefire mediation has led to renewed fighting in the north of the country, and the rebels are advancing on the key cocoa-growing centres.

Too close for comfort

Speaking to the Reuters news agency, exporters said the rebels' advance risked cutting off not only cocoa supply lines, but also the lines of credit arranged through banks in the afflicted areas.

The town of Vavoua, only 60 kilometres from the key central cocoa town of Daloa, fell to the rebels on Monday.

"Vavoua is on the fringe of the cocoa belt, and it's not at all good," one exporter in Abidjan, the commercial capital, told Reuters. "We're nervous."

Others warned that they were planning to limit the amount of money they sent up-country to finance purchases.

The key shipping season runs from October to December.

Conflicting claims

So far, government forces have apparently had little success in dislodging the hold of the rebels - largely disgruntled soldiers facing demobilisation - over the whole of the Muslim-dominated north of the country.

An attempt to push them out of their stronghold at Bouake in the north failed early on Tuesday, according to eyewitness reports carried by news agencies.

The 500,000-population city was taken by the rebels on 19 September.