Luanda - More than 150 North Korean labourers have left Angola following tightened sanctions against the pariah state, the southern African country said on Tuesday.Angola's foreign minister Manuel Augusto told state TV the 154 guest workers, who had been working on construction projects, left on Sunday and Monday.They had been employed by North Korean building company Mansudae, which also builds monuments under the terms of a cooperation deal between the two countries.Augusto said his country needed to meet "international obligations"."As their contract had finished, we saw no reason why they should stay in the country," he said.Angola is one of 11 African countries suspected by the United Nations of maintaining military ties with Kim Jong-un's regime - including training exchanges between police and military units.In an update published in September, UN experts said they had received no response from Luanda to the allegations of cooperation with Pyongyang.Angola's foreign minister vowed to respect UN Security Council resolution 2 371 which imposes tough sanctions on North Korean companies in response to Pyongyang's repeated missile tests and nuclear programme."We have international obligations that we have to meet," said Augusto."But that doesn't mean we sever our ties with North Korea. It's an ally that has historically been with our country so our relations with North Korea will remain."North Korea forged friendly relations with several African nations during their wars of independence and during the Cold War.