Abuja, June 2 : Nigerian President Muhammadu Buhari on Tuesday further called for joint international efforts to tackle the Covid-19 pandemic and the consequent challenges. "The unprecedented crisis brought by the Covid-19 pandemic has now caused far more serious setbacks to our quests for sustainable development, hence the need for international cooperation and collaboration to fight the disease, as no country is immune from its devastating effects on lives and livelihoods," said Buhari. The Nigerian leader made the remarks at a ceremony to receive credentials from foreign diplomats at the State House, the Xinhua news agency reported. "As you all settle down to your solemn duties to promote your respective national values and interests through your countries' foreign policy on Nigeria, you should rest assured that the Federal Republic of Nigeria will engage you as we all strive to relate through effective cooperation and collaboration to enhance our collective interests," he said. The bilateral relations between Nigeria and each of the countries were most cordial, said Buhari. "We still need to enhance these fraternal ties between our nations." /IANS