Sudan leader says he will teach independent South a 'final lesson by force' Abd Raouf / AP Sudanese President Omar al-Bashir, center, waves from the back of a truck during a visit to North Kordofan, Sudan, Thursday, April 19, 2012. The Arab League said Thursday it would hold an emergency meeting over the increasing violence between Sudan and South Sudan. KHARTOUM, Sudan -- Sudan's President Omar Hassan al-Bashir all but declared war against his newly independent neighbor on Thursday, vowing to teach South Sudan a "final lesson by force" after it occupied a disputed oil field. South Sudan accused Bashir of planning "genocide" and said it would fight to protect its people. Mounting violence since Sudan split into two countries last year has raised the prospect of two sovereign African states waging war against each other openly for the first time since Ethiopia fought newly independent Eritrea in 1998-2000. Both are poor countries - South Sudan is one of the poorest in the world - and the dispute between them has already halted nearly all the oil production that underpins both economies. South Sudan says Heglig oilfied reduced 'to rubble' Appearing in medal-spangled military uniform at a large rally, Bashir danced side-to-side, waved his walking stick in the air and made blistering threats against the leadership of the South, which seceded last year after decades of civil war. "These people don't understand, and we will give them the final lesson by force," the burly military ruler told the rally in El-Obeid, capital of the North Kordofan state. We will not give them an inch of our country, and whoever extends his hand on Sudan, we will cut it off. China, a major investor in the oil industry in both countries, expressed "serious concern" about the increase of tensions and called on both sides to stop fighting, "maintain calm and exercise maximum restraint." Adriane Ohanesian / AFP - Getty Images A picture taken on April 17, 2012 shows burned buildings which are all that remain of an old Sudan Armed Forces (SAF) compound in Heglig, in Sudan. U.N. Secretary-General Ban Ki-moon said South Sudan's seizure of the oil field was an "illegal act" and called on both countries to stop fighting. Bashir: South Sudan rulers are 'insects' South Sudan separated from the rest of Sudan with Bashir's blessing last July under the terms of a 2005 peace deal. But since then violence has steadily escalated, fuelled by territorial disputes, ethnic animosity and quarrels over oil. Birthday wish: 'Lost boys' pin hopes on independent South Sudan Last week, South Sudan seized Heglig, a disputed oilfield near the border between the two countries, claiming it as its rightful territory and saying it would only withdraw if the United Nations deployed a neutral force there. Sudan's armed forces spokesman Al-Sawarmi Khalid said by phone the army was now fighting "inside Heglig." South Sudan's army (SPLA) said it had repulsed a large attack on Heglig on Wednesday evening, stopping Sudan's forces about 18 miles from the territory. "The SPLA maintained its position," spokesman Philip Aguer said. He also accused Sudan of launching another attack in the border regions of South Sudan's Western Bahr al-Ghazal state. In a sign of the conflict widening, the Justice and Equality Movement (JEM) - considered the most militarily potent of the rebel factions in Sudan's western Darfur region - claimed it had launched an assault on the al-Kharsana oil region near Heglig. PhotoBlog: Last few licks of paint as South Sudan preps for independence "We are surrounding the Sudanese army in the main military base in al-Kharsana," JEM spokesman Gibreel Adam Bilal said by phone. Heglig is hundreds of km away from JEM's bases in Darfur but the group has fought in the Kordofan region in the past. The Sudanese army spokesman, Khalid, denied JEM's statement, saying there was no fighting in the al-Kharsana area. Limited access for independent journalists to Sudan's remote conflict zones makes it difficult to confirm the often contradictory claims issued by all sides. Sudanese Lost Boy Mawut Mayen talks about his life in America and what the new nation of South Sudan means to him. African states have often waged war on each other's territory, but it is extremely rare for them to talk openly of fighting against government forces of sovereign neighbors. Bashir's address to the rally on Thursday followed a fiery speech to party supporters on Wednesday, when he vowed to "liberate" South Sudan from its ruling party, which he repeatedly referred to as "insects," in a play on its Arabic name. South Sudan's Information Minister Barnaba Marial Benjamin responded on Thursday with outrage. Mr. President, we are no insects and if you are launching your genocide activities to the Republic of South Sudan to kill the people of South Sudan .... we can assure you we will protect the lives of our citizens. However, he also said South Sudan was willing to resume talks immediately on all outstanding issues. "The Republic of South Sudan is not in a state of war, nor is it interested in war with Sudan," he said. In both speeches, Bashir vowed to retake the Heglig oilfield, which he said was part of Sudan's Kordofan region. But he also said that alone would not end the conflict. "Heglig is not the end, but the beginning," he said in Thursday's speech.