KHARTOUM - Sudan's President Omar Hassan al-Bashir threatened 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. Appearing in medal-spangled general's uniform at a large rally in the border province of North Kordofan, the burly military ruler danced side-to-side, waved his walking stick in the air and made blistering threats against the leadership of the South, which broke off last year after decades of civil war. "These people don't understand, and we will give them the final lesson by force," Bashir told the rally in El-Obeid, North Kordofan's capital. "We will not give them an inch of our country, and whoever extends his hand on Sudan, we will cut it." 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. Last week, South Sudan seized Heglig, a disputed oil field 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. Bashir vowed to retake the oil field, which he said was part of Sudan's Kordofan province. That alone would not resolve the conflict, he added. "Heglig is not the end, but the beginning." Global powers have voiced alarm at the escalation of violence and urged the two to stop fighting and return to talks. In a dramatic escalation of rhetoric on Wednesday, Bashir said he would "liberate" South Sudan from its rulers, the Sudan People's Liberation Movement, which fought the guerrilla civil war against Khartoum. There was no immediate comment from the South to Thursday's speech. China, a major investor 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".