KHARTOUM - The Sudanese army announced on Tuesday that troops from South Sudan had launched a large-scale attack on a strategic oil filed on the borders between the two countries.

The Sudanese Armed Forces (SAF) said in a statement that troops of the Sudan People's Liberation Army (SPLA) carried out a large- scale assault on Heglig oil field in South Kordofan State bordering South Sudan.

Heglig is the largest oil filed in Sudan, which products roughly half of Sudan's 115,000 barrel a day output.

"The malicious forces belonging to South Sudan violated our southern border towards the city of Heglig, and these forces consisting of SPLA elements and mercenaries from inside the State of South Sudan have moved (into Sudan's territories), led by hatred, ill will and a desire rooted in the continuing war," said the statement, a copy of which was attained by Xinhua.

"We promise our people a new victory on remnants of treachery and betrayal in the battle, in which all the enemies of the country will pay their prices," the statement added.

South Sudan said earlier Tuesday that Sudan had attacked a disputed oil-producing border region with warplanes and artillery, noting that the town of Teshwin in the border area had come under attack late Monday and that fighting was continuing on Tuesday.

"They launched a new attack, and occupied southern territory until the SPLA repulsed them," said SPLA spokesman Philip Aguer in a statement.

He said the Sudanese ground forces had started their attack from Heglig.

Meanwhile, the Paris-based Sudan Tribune website reported that SPLA forces had claimed the capture of the Heglig town Monday afternoon after repulsing an attack by the SAF troops.

SPLA Division Four commander James Gatduel Gatluak was quoted as saying that the SAF had launched air and ground attacks, forcing them to engage fighting with the Sudanese troops to take control of Heglig on Tuesday.

The SPLA general further alleged that their troops were advancing about 30 km north of the Heglig oil field.

The two countries are at odds over how much the landlocked South Sudan should pay to export its oil through Sudan.

South Sudan took three quarters of what was the united country' s oilput when it seceded in July 2011. It shut down production in January after Khartoum confiscated some of its oil for what it alleged unpaid transit fees.

Sudanese President Omar al-Bashir had been scheduled to meet his South Sudanese counterpart Salva Kiir in Juba, capital of South Sudan last week to defuse tension, but he called off the summit following the border clashes.

Among other unresolved issues, the two sides need to demarcate their borders and end accusations of supporting rebels in the other's territories.