RUBKONA, South Sudan — Sudanese warplanes bombed a market and an oil field in South Sudan on Monday, killing at least two people after Sudanese ground forces had reportedly crossed into South Sudan with tanks and artillery, elevating the risk of all-out war between the two old enemies.

The international community urged Sudan and South Sudan to talk out their disputes, which include arguments over where the border lies and over ownership of oil resources.

U.N. Secretary-General Ban Ki-moon condemned the Sudanese bombings and called on the government in Khartoum “to cease all hostilities immediately,” U.N. deputy spokesman Eduardo del Buey said.

Ban stressed again that the dispute cannot be solved militarily and urged Sudanese President Omar al-Bashir and South Sudan’s President Salva Kiir “to stop the slide towards further confrontation and … return to dialogue as a matter of urgency,” the spokesman said.

But al-Bashir vowed Monday to press ahead with his military campaign until all southern troops or affiliated forces are chased out of the north.

The bombs fell from two MiG 29 jets onto Rubkona’s market with a whistling sound, turning stalls where food and other household items are sold into fiery heaps of twisted metal.

The burned body of the boy lay flat on his back near the center of the blast site, his hand clutching at the sky.

South Sudan military spokesman Col. Philip Aguer said two were killed in that attack and nine wounded.

Aguer said Antonov bombers accompanied by MiG 29 jets also bombed Abiemnom in Unity State and the Unity State oil field. He said Abiemnom is a two-hour drive from Rubkona. Amid poor communications, the extent of damage at the oil field was not immediately known, nor whether there were casualties. Fighting between ground troops, which started Sunday, was still ongoing in Panakuac, Laloba and Teshwin, Aguer said.

In Rubkona, trucks packed with South Sudanese troops sped off in the direction where the bombs landed as the soldiers fired at the Sudanese jets.

“The bombing amounts to a declaration of war,” said Maj.

Gen. Mac Paul, the Deputy Director of Military Intelligence for South Sudan.

U.S. State Department spokeswoman Victoria Nuland said Monday the U.S. strongly condemns Sudan’s military incursion into South Sudan, and called for the immediate halt of aerial and artillery bombardment in South Sudan.

“We recognize the right of South Sudan to self-defense and urge South Sudan to exercise restraint in its reaction to Sudan’s attack in Unity State,” she said.

Sudanese armed forces launched an attack Sunday more than six miles inside South Sudan’s border, even though the south announced on Friday it was pulling its troops from the disputed oil town of Heglig to avoid an all-out war. South Sudan had invaded Heglig earlier this month, saying it belonged to the south.

South Sudan broke away from Sudan in July last year after an independence vote, the culmination of a 2005 peace treaty that ended decades of war that killed more than 2 million people.d