China's foreign ministry on Sunday urgently summoned a senior Angolan diplomat, to protest Angola's mass arrest of Chinese citizens on Friday.

Angolan police arrested hundreds of Chinese citizens without first verifying their identities in an operation that aimed to investigate illegal immigration on Friday, the Xinhua News Agency reported.

The detainees also include citizens of Portugal and the Democratic Republic of the Congo.

Lin Songtian, director of the African Affairs Department of the Ministry of Foreign Affairs, said that Angolan police indiscriminately arrested and detained hundreds of Chinese citizens, which undermined the legitimate rights and interests of Chinese nationals and created panic among law-abiding Chinese companies and citizens.

China has expressed "grave concerns" over the incident, urging the Angolan government to properly deal with the more than 30 Chinese citizens that are still being detained, as soon as possible and according to the law, Lin said, adding that Angola should fully guarantee that they will be treated humanely.

Most of the Chinese citizens that provided legal documents proving their right to be in the country have been released.