An Egyptian former diplomat was detained by authorities in Cairo on Thursday, just two weeks after calling for a referendum on President Abdel Fattah el-Sisi’s government.

“Security forces took my father, Maasoum Marzouk, from our home without explanation and without cause just for practicing his constitutional rights of calling for a referendum,” Maisara Marzouk said.

“A minibus of around 15 civilian-dressed, armed security personnel arrived at 1pm and arrested him, then searched his house and took his personal belongings without showing us the legal permit for that procedure,” she added.

Marzouk is a former ambassador and assistant minister of foreign affairs. He is renowned for his criticism of the Sisi government. He recently founded The People’s Democratic Party, an opposition party.

Egyptian authorities have not informed Marzouk’s lawyer or family members of any charges that he faces. They believe he is being interrogated for his calls for a national referendum on the president.

In a statement issued on August 5, Marzouk called for a public referendum to answer one question: “Do you accept that the current regime stays in power?”

Michael Page, deputy director of the Middle East and North Africa division at Human Rights Watch said that Marzouk’s arrest in Egypt “appears to be the latest in an unending wave of repression against anyone who dares to criticize President Abdel Fattah el-Sisi.”

“Due process, fair trials, access to a lawyer — all these fundamental rights are regularly denied to the tens of thousands of people El-Sisi has now had arrested with impunity,” Page said.

Egyptians Abroad For Democracy Worldwide, a monitoring group based in the US, also condemned the arrest of Marzouk.

Sisi was elected to a second term in office in April, securing 97% of the vote, according to Egypt’s National Election Authority.