* United Nations says 14 missing from bombing of camp
* Rebels say Khartoum launched second attack north of border
* Incident deepens arguments over oil revenues (Adds South Sudan comment, background)
By Tom Miles and Hereward Holland
GENEVA/JUBA, Jan 24 An air strike on a refugee camp near South Sudan's border with Sudan wounded one boy and left 14 people missing on Monday, the U.N. refugee agency said.
South Sudan blamed the attack on Khartoum, which has repeatedly denied carrying out such strikes on its neighbour.
South Sudan seceded from Sudan in July under a 2005 peace deal that ended decades of civil war, but the two countries have remained at loggerheads over issues including oil, debt and fighting along the poorly drawn border.
Several bombs were dropped on Elfoj, a camp of about 5,000 refugees used as a transit site, less than 10 km from the border on Monday morning, a spokeswoman for the U.N. High Commissioner for Refugees (UNHCR) said in a statement on Tuesday.
"Definitely it is Khartoum forces ... there is no one else who can bombard South Sudan's territory," a South Sudan military spokesman said of the attack on Elfoj. "This is not the first time."
Rebels fighting Khartoum's forces said Sudanese government helicopters and ground forces launched separate attacks on the Sudan side of the border on the same day, although the report was impossible to verify independently.
Sudan's military was not immediately available to comment on either incident, but Khartoum has always denied carrying out such attacks, including one on the Yida refugee camp in November, which the United Nations blamed on Khartoum.
Fighting between Khartoum's forces and rebels from the Sudan People's Liberation Army/Movement-North (SPLA/M-N) began in June, before South Sudan became independent in July, and have forced around 417,000 people to flee their homes and 80,000 to cross the border into South Sudan, and into camps such as Elfoj.
The SPLM is now the ruling party in South Sudan but it denies supporting SPLM-N rebels across the border.
The insurgency against Khartoum is a remnant of a two-decade civil war in which many in Blue Nile and South Kordofan states fought with those now ruling South Sudan but ended up falling under Khartoum's control.
However, fighting around the border also feeds into wider animosity over issues including the division of revenues from oil from South Sudanese fields which is exported through Sudan.
UNCHR did not apportion blame. It moved 1,140 people from the site, around 70 km (45 miles) to the south after the air strike.
Details about what the South Sudanese spokesman described as the attack on rebels in the south of Sudan were sketchy but a U.N. source confirmed it had received reports of two helicopters attacking the Ullu area near the border.
An SPLM-N spokesman told Reuters the settlement of Danfona, just across the border from Elfoj, had been bombed.
"There is a big movement of Sudan Armed Forces from (Blue Nile state capital) al-Damazin towards the Bau mountains. They are coming with heavy weapons and air cover from helicopter gunships," the spokesman told Reuters by telephone.
Tension between Sudan and South Sudan further escalated on Monday when South Sudan began shutting down oil production, accusing Sudan of stealing $815 million worth of crude that it piped to its northern neighbour for shipment. (Writing and additional reporting by Alexander Dziadosz and Ulf Laessing; Editing by Stephanie Nebehay and Ben Harding)