Algeria's richest man Issad Rebrab has been detained in jail on the public prosecutor's orders, state media reported Tuesday, a day after his arrest as part of a corruption probe.
The crackdown on alleged graft follows the resignation of veteran president Abdelaziz Bouteflika in early April after weeks of mass protests against his 20-year rule.
News of Rebrab's arrest came as thousands of students thronged the capital's streets calling for the overthrow of the "system" and for trials against members of the deposed leader's inner circle.
Late on Tuesday, state television also announced the head of Algeria's vital state-owned oil giant Sonatrach had been sacked.
Abdelmoumen Ould Kaddour, who had headed the firm since 2017, was replaced by Rachid Hachichi on the orders of the country's interim President Abdelkader Bensalah, it said, without giving details on why.
Rebrab, the 74-year-old chief executive of Algeria's biggest privately-owned conglomerate Cevital, was placed in detention overnight, the APS news agency reported.
Forbes lists Rebrab as Algeria's richest man and the sixth-wealthiest in Africa, with a net worth of $3.38 billion.
He is "suspected of having made fake statements concerning the transfer of funds to and from abroad", APS reported.
He is also suspected of importing "used equipment" despite enjoying tax and tariff breaks intended for the purchase of new products.
On Monday, Rebrab tweeted that he had gone voluntarily to a police station to discuss "equipment that has been held up at the Algiers port since June 2018".
Cevital, which he founded, employs 18,000 people, produces electronics, steel and food, and in recent years acquired businesses in France.
Forbes reports Cevital also owns one of the world's largest sugar refineries, capable of producing two million tonnes a year.
But while his business activities flourished under Bouteflika's rule, Rebrab has had a tense relationship with the ruling circle.
He has been in open conflict with Algerian authorities since 2015, accusing them of blocking his investments in the country.
Last month he threw his support behind the anti-Bouteflika protests.
Rebrab is one of a number of tycoons detained in graft investigations since the 82-year-old president stepped down.
The arrests come after army chief Ahmed Gaid Salah called on prosecutors to "accelerate the pace" of corruption probes into those with ties to Bouteflika's inner circle.
Late Sunday four brothers from the influential Kouninef family were arrested, according to state television, in relation to a probe into non-compliance with state contracts.
Prosecutors are investigating "insider influence to obtain undue advantages and misappropriation of real estate," according to the broadcaster.
Abdelkader, Reda, Karim and Tarek Kouninef have dealings in everything from agribusiness to civil engineering.
The family is said to be close to Said Bouteflika, the younger brother and former advisor of the deposed leader.
Algerians have kept up protests since Bouteflika stepped down, calling for a complete overhaul of Algeria's political system including the ouster of an interim government set up in his wake.
They are demanding that regime stalwarts be excluded from any political transition in the country, where presidential elections are due to take place on July 4.
Crowds of students gathered in the heart of the capital earlier in the day chanting "out with the government" and the "gang" ruling the country.
"Either it's us, or it's you. Out with the government!" cried the students, many of them drapped in Algeria's national flag.
"We want a new system that is committed to fighting the corruption that has plagued the country," said Hamid, a finance student in Algiers.
On Tuesday army chief Salah praised "the judiciary's response... which will reassure the people that its looted money will be recovered by force of law and with the requisite rigour".
On Monday state television reported the current finance minister, Mohamed Loukal, and former prime minister Ahmed Ouyahia had been summoned for questioning by a magistrate in connection with the alleged misuse of public funds.
The latest developments follow the arrest late last month of Ali Haddad, one of Algeria's top businessmen and a Bouteflika backer, who had tried to cross the border into Tunisia with two passports and undeclared currency.
The day after he was detained, prosecutors announced graft probes into unnamed individuals and banned corruption suspects from leaving the country.
Algerian media has reported around a dozen businessmen are under investigation, all with ties to Bouteflika's entourage.