China on Wednesday offered a spirited defence of its aid to Africa, rejecting charges of "concrete diplomacy" following a major infrastructure deal with the continent.

China and the African Union announced Tuesday an ambitious plan to develop road, rail and air transport routes to link capitals across the continent, though few details were released and the deal was described as a commitment to develop the infrastructure.

The memorandum of understanding (MOU) was signed at AU headquarters in Addis Ababa, ahead of a summit meeting of the leaders of the 54-nation pan-African bloc on Friday.

China is the continent's largest trading partner.

Foreign ministry spokeswoman Hua Chunying defended Beijing's role when asked to comment on accusations that China's infrastructure projects in Africa amounted to "concrete diplomacy" and sought only to extract the continent's resources.

"A well functioning road will lead wealth to your place," she said, adding that projects under the MOU will help African countries "enhance their connectivity" and "break their development bottleneck".

China had completed 1,046 projects in Africa, building 2,233 kilometres of railways, 3,530 kilometres of roads and 132 schools and hospitals, she said.

"We hope that more countries can act like China to demonstrate their sincerity and do something really good for African countries," she added.

African Union chief Nkosazana Dlamini-Zuma praised the MOU on Tuesday as "the most substantive project the AU has ever signed with a partner".

Africa is in dire need of better transport infrastructure, and the the quickest route to get from one side of the continent to the other can involve flight connections via Europe.