South Sudan has accused Sudan of launching further bombing raids on its territory and against its forces.
The governor of Unity state says several people were killed in its capital Bentiu when a plane dropped bombs on a market.
South Sudan also says its troops came under air attack in the oil-producing Heglig region which they have seized.
Sudan's ambassador to the UK, Abdullahi Al Azreg, said Sudan did not target civilians.
South Sudan may have won independence and a seat in the United Nations, but the geography is one of dependence on Sudan:
SOURCE: From the article above
Until that proposed pipeline can be built through a friendly Kenya, Sudan has a choke hold on South Sudan:
The outcome of the dramatically escalating border fighting between Sudan and South Sudan is more likely to be determined by which of the two faltering economies collapses first than by relative military prowess.
South Sudan, which seceded from Sudan in July, seized the disputed Heglig oilfield on Tuesday, edging the two former civil war foes closer to full-blown conflict than any time since the South gained independence.
But rather than sparking an all-out military confrontation, each side's aim may now be to target one another's oil facilities and wait for their opponent to crumble under armed insurgencies, popular unrest and fuel shortages.
"It is a question of which side can maintain the basic governance and military structures longer," a Sudan expert with government contacts said, speaking on condition of anonymity.
Sudan may have more military power than South Sudan, but South Sudan is only the most successful of several insurgencies to challenge the central government of Sudan. But South Sudan is dirt poor.
South Sudan may have taken a disputed region, but Sudan has been aggressive and punitive with South Sudan since the latter gained independence. South Sudan better hope the Arab Spring reaches Khartoum, because membership in the United Nations and a dollar will get South Sudan a small cup of coffee, it is clear.
UPDATE: Sudan vows to retake the disputed region that South Sudan seized:
"Despite the high cost of the war, despite the destruction that the war can cause ... our options are very limited. We can tolerate some sacrifice, until we can liberate our land," Sudan's ambassador to Kenya, Kamal Ismail Saeed, said.
"So from our side, yes, it is expensive but that doesn't deter us or that doesn't stop us from exerting all effort to liberate our land," he told reporters in Nairobi.
South Sudan is foolish. Sudan can count on China for weapons and support until Sudan captures the oil wells. Who does South Sudan think is going to save them?
And the sight of two dirt-poor nations squandering the chance of oil money making them a little less dirt poor is depressing.
UPDATE: Fighting is spreading:
Sudan and South Sudan accused each other of launching attacks on a new front near their contested border, stoking fears of a return to all-out war in the oil-producing region.
The reports of the fresh fighting south of the Sudanese town of Mairem late on Tuesday came as the UN Security Council discussed imposing sanctions on the African neighbours if they did not stop the escalating border clashes.
South Sudan is foolish to provoke fighting with their stronger neighbor by trying to win a conventional clash. They just risk giving Sudanese actions enough justification to allow Sudan to really pound South Sudan with impunity.
