Warplanes bombed a refugee camp in South Sudan Thursday, an attack local officials blamed on neighboring Sudan.

A local journalist told VOA that planes bombed the Yida refugee camp in South Sudan's Unity state Thursday afternoon.

The commissioner of local Pariang County, Miabek Lang, told reporters that 12 people were killed and at least 20 wounded in the bombing. However, other reports from the area said there were no casualties.

Sudan's armed forces denied bombing South Sudan's territory.

The two countries have been at sharp odds over several issues since the south became independent in July.

Speaking to reporters Thursday, South Sudan's President Salva Kiir denied accusations that his country is supporting rebels fighting the Sudanese government.

He also suggested that Sudanese President Omar al-Bashir is planning to invade and retake South Sudan.

Sudan has accused the south of supporting rebels in two states along the border, Southern Kordofan and Blue Nile. Yida, which sits about 40 kilometers from the border, hosts thousands of refugees from Southern Kordofan.

Late Wednesday, the United States strongly condemned a separate airstrike in South Sudan.

Southern leaders say Sudanese jet fighters bombed an area of Upper Nile state on Monday, killing seven people.

The U.S. State Department called the attack provocative, and said such bombardments increase the chance of war between Sudan and South Sudan.

Sudan has recognized the south's independence but the sides have yet to resolve issues over borders — especially in the oil-rich Abyei region — and the sharing of oil revenue. The south took over most of Sudan's oil in the split but pipelines to the sea run through the north.