MADRID/BEIJING (Reuters) - Spanish police have arrested a sixth worker at the Madrid branch of Industrial and Commercial Bank of China (ICBC) , a source close to the investigation said on Friday (Feb 19), after five directors were detained in a raid on Wednesday.

The five directors, including the Madrid branch's general manager, are due to testify in a Madrid court on Friday morning facing charges of money laundering, fraud and tax crimes, according to a legal source.

A Chinese foreign ministry official emphasised on Friday that China attaches high importance to a case involving the Madrid arrests.

Liu Haixing, assistant foreign minister, met Jose Luis Garcia Galan of the Spanish embassy on Friday, the Foreign Ministry said in a brief statement on its website.

Liu asked that Spain protect the rights and interests of Chinese firms and citizens there and handle the case in accordance with the law, the ministry said.

A Beijing-based spokesman for ICBC has said its Madrid branch was cooperating with the investigation.

The Spanish embassy in Beijing did not immediately respond to telephone calls from Reuters to seek comment on the details of the meeting.

China's large state-owned lenders have been dogged by allegations of improper conduct as they expand abroad.

The probe into ICBC by police, the Spanish tax agency and Europol involves funds handled by a criminal group that the Interior Ministry says passed through the bank and were transferred to China.