South Sudan on Sunday accused Sudan of bombing its side of their volatile border, killing one soldier and wounding four others in what it said was the third attack on its northeastern Renk County since November.
Sudan's army spokesman al-Sawarmi Khalid denied the accusations, as it has each time South Sudan has alleged an attack. Reuters reporters have witnessed several air strikes against South Sudan since it seceded from Sudan in 2011.
The African neighbors have been at loggerheads over oil, territory and other disputes and came close to war in April. Neither has implemented a deal signed in September calling for the creation of a buffer zone and resumption of oil exports.
South Sudan's army (SPLA) said it repulsed a Sudanese helicopter attack early on Saturday morning at a water-point near Babaniss, in the oil-producing Upper Nile state.
"At 10:30 (Sudanese Armed Forces) SAF attacked with two helicopter gunships, killing one SPLA and injuring three," SPLA spokesman Philip Aguer said.
Sudanese warplanes wounded another SPLA soldier in a second air raid at mid-day, some 21 km (13 miles) inside South Sudanese territory, according to Aguer.
Talks between the Presidents of Sudan and South Sudan ended without a breakthrough in Ethiopia's capital last month, further delaying the restart of the landlocked South's oil industry after a year-long shutdown.
"Their plan is to escalate the conflict so the people always discuss new issues and postpone implementation of the agreements," Aguer said.
South Sudan, which inherited three-quarters of the former unified nation's oil production when it broke away, shut down its entire output of 350,000 barrels a day in January 2012 after tensions over pipeline fees escalated.
Sudan accuses South Sudan of supporting rebels who operate in two states on the border with South Sudan. Juba denied the charge and accuses Khartoum of backing rebels on its territory.