Despite the threats and hostilities, a southern government spokesman said South Sudan was only defending its territory and considers Sudan a “friendly nation.”

South Sudan military spokesman Col. Philip Aguer said three of the attacks were on Wednesday and one was on Thursday. He did not give a death toll.

South Sudan broke away from Sudan last year after a self-determination vote for independence. That vote was guaranteed in a mediated end to decades of civil war between the two sides. But the sides never fully agreed where their shared border lay, nor did they reach agreement on how to share oil wealth that is pumped from the border region.

Instead, the two countries have seen a sharp increase in violence in recent weeks, especially around the oil-producing town of Heglig. Both sides claim Heglig as their own. It lies in a region where the border was never clearly defined.

Aguer said southern troops repulsed one attack by Sudanese troops near Heglig on Wednesday and two attacks in Northern Bahr el Ghazal state. One was repulsed in Western Bahr el Ghazal state early Thursday, he said.

Sudan President Omar Bashir on Wednesday threatened to topple the South Sudan government after accusing the south of trying to take down his Khartoum-based government. Bashir continued his hard-line rhetoric on Thursday in an address to a “popular defense” brigade headed to the Heglig area. The ceremony was held in Al-Obeid, in northern Kordofan.

“Sudan will cut off the hand that harms it,” said Bashir, a career army officer who fought against the southern army, the Sudan People’s Liberation Army, during the 1983-2005 civil war. Bashir seized power in a 1989 military coup.

The capture of Heglig by the South Sudanese “has revived the spirit of jihad and martyrdom among the Sudanese people,” he told the brigade’s 2,300 men, according to the official Sudan News Agency.

In Khartoum, the pro-government Sudanese Media Center said late Wednesday that fighting broke out between the two nations in the Al-Meram area in South Kordofan, with northern troops driving away what it called “remaining elements” of the SPLA. It said northern troops chased away SPLA fighters who fled across the border into South Sudan.

It said the fighting left an unspecified number of dead and wounded among the SPLA forces but gave no precise figures.