SPLA Commander in South Sudan, Yusef Kua

The rebel Sudan People's Liberation Army (SPLA) said it had repulsed a counter-attack by two government brigades with a combined strength of about 3,000 soldiers in the eastern Blue Nile province.

Attempt to recapture towns

The BBC East Africa correspondent says the aim appears to have been to try to recapture towns lost earlier this month in the eastern province of Blue Nile.

On Thursday, the Sudanese President Omar al-Bashir, visiting the second largest town in the south, said his government was determined "to free all regions occupied by the rebels, peacefully or by force".

SPLA claims strategic gains

The SPLA in the Kenyan capital, Nairobi, said that the rebels destroyed two tanks and captured another, along with other equipment and enough food to feed one brigade throughout the coming rainy season.

The claimed victory opens the road for a rebel push from the south towards the hydroelectric dam at Damazin, which supplies power to the capital, Khartoum. Blue Nile province is also the back door to the oil producing area of Bentiu.

Unusually large battle

Listen to BBC's Martin Dawes report from Nairobi (1' 16")

The BBC correspondent says sizeable military clashes have not been regular events in the 15-year-old civil war.

However there has been an upsurge since last month's peace talks in which both sides accepted a referendum on independence for the south, without agreeing a timetable.

Risk of famine remains

Apart from the clashes in Blue Nile, pro-government militia have been attacking into northern Bahr-el-Ghazal, a region which is the focus of an international relief effort.