Fatou Bensouda. [Photo/Agencies]

BRUSSELS - The sanctions announced by the US administration against two staff members of the International Criminal Court (ICC), including its prosecutor, are "unacceptable", the European Union (EU) announced on Thursday.

The sanctions are "unprecedented measures that attempt to obstruct the Court's investigations and judicial proceedings," Josep Borrel, the EU high representative for foreign affairs and security policy, said in a statement.

The US on Wednesday imposed sanctions on ICC Prosecutor Fatou Bensouda and a senior staff member in her office for continuing to investigate war crimes allegations against Americans. It has been reported that the sanctions include a freeze on assets held in the US or subject to US law.

"The United States should reconsider its position and reverse the measures it has taken. Impunity must never be an option," said Borrel.

United Nations Secretary-General Antonio Guterres on Wednesday also noted "with concern" the imposition. On behalf of the UN chief, spokesperson Stephane Dujarric said "we continue to closely follow developments on this matter".

The ICC in March authorized an investigation into possible war crimes in Afghanistan, including those that may have been committed by the US military and the Central Intelligence Agency, which could lead to the indictment of US military and intelligence personnel.