Nigerian President Olusegun Obasanjo arrived here Thursday morning, starting a four-day state visit to China as guest of Chinese President Hu Jintao.

China and Nigeria signed five economic agreements 15th night, promising to upgrade their relations to a "strategic partnership."

The five agreements, covering investment, telecommunication service and technical cooperation, were signed after an hour-long talk between Chinese President Hu Jintao and Nigeria President Olusegun Obasanjo, who is in China for a four-day state visit.

China and Nigeria set up full diplomatic ties in 1971 and the trade volume between the two countries reached 2.18 billion US dollars. Nigeria is now China's second largest export market and fourth largest trade partner in Africa.

During talks with Obasanjo, Hu suggested the two sides take active measures to expand the economic and trade cooperation and further boost two-way investment.

He expressed hope that the two sides will improve cooperation in gas exploration, infrastructure construction and manufacturing industry to achieve common development.

He suggested the countries enhance political trust through high-level visits and personnel exchanges, improve consultation and coordination in international affairs and join hands to maintain the interests of developing countries, boost south-south cooperation and promote the establishment of a fair and reasonable new international political and economic order.

Obasanjo said he agreed with Hu. He said Nigeria is now undergoing reforms to realize economic and social development.

Nigeria hopes the two sides will improve mutually beneficial cooperation in the fields of trade, investment, electric power, railway and telecommunication construction, agriculture, water conservancy, manufacturing and tourism, he said.

On the issue of China-Africa relations, Hu said the African Union is playing an increasing important role in regional affairs and the dialogue and cooperation between Africa and the international community is deepening.

Hu said improving cooperation with African countries is China's strategic choice. He highlighted the role of China-Africa Cooperation Forum in enhancing China-Africa friendship, saying that China will work together with the African countries to further promote the new China-Africa strategic partnership.

Obasanjo, who is also visiting China in the capacity of rotating president of the African Union, said the African people will never forget China's support in their struggle against colonialism and racial segregation.

He said Africa hopes China will support and join Africa's efforts in seeking a solution to the conflicts in the region and improving investment and economic cooperation with Africa to help it achieve peace, security and development soon.

During the talks, Hu expressed China's appreciation for Nigeria's consistent adherence to the one-China policy and its support to China's adoption of the Anti-Secession Law.

Obasanjo said Nigeria firmly abides by the one-China policy and supports China's cause of national reunification.

Obasanjo arrived in Beijing on Thursday morning as Hu's guest. Besides Beijing, Obasanjo will also travel to Hubei Province and Shanghai.