Turkey’s president has accused the political opposition of “sinking the economy” during the country’s biggest protests in more than a decade following the arrest of Istanbul’s mayor, Ekrem İmamoğlu.

Recep Tayyip Erdoğan’s comments come after İmamoğlu’s Republican People’s Party (CHP) called for a boycott of companies it says support the government.

Erdoğan said the opposition is “so desperate that they would throw the country and the nation into the fire”.

In an address to lawmakers of the ruling Justice and Development Party (AK Parti), Erdoğan added that “sabotage targeting the Turkish economy will be held accountable before the courts”.

İmamoğlu, who was arrested a week ago, faces charges related to corruption and supporting a terrorist group within the Istanbul municipality alongside 90 other suspects.

A court ordered him to be imprisoned on Sunday. A trial date has not been announced.

Many consider the case against İmamoğlu, seen as the biggest challenger to Erdoğan’s 22-year rule, to be politically motivated, but the government says the judiciary is free of political influence.

The evidence against İmamoğlu has not been officially disclosed. Many Turkish media outlets have reported that it is largely based on “secret witnesses”.

The use of such testimony has been seen in previous criminal cases against opposition politicians.

The head of the opposition Iyi Party, Musavat Dervişoğlu, questioned the dearth of public evidence relating to the corruption charge.

“Dozens of inspectors have gone, 1,300 inspections have been made, nothing has come out of these inspections,” he told his lawmakers.

Members of Istanbul’s municipality voted on Wednesday for a proxy mayor to stand in for İmamoğlu, with CHP party members choosing Nuri Aslan, İmamoğlu’s deputy.

While the CHP has said it will no longer organise mass rallies at City Hall, students across Turkey have continued to protest.

Demonstrations in Istanbul, Ankara and Izmir, as well as smaller cities and towns, have been largely peaceful with protesters demanding İmamoğlu’s release and an end to democratic backsliding.

Interior Minister Ali Yerlikaya has said that 1,418 people have been detained in the past week in connection with the protests.

Egitim-Sen, a trade union representing teachers and university lecturers, said its Istanbul University representative had been detained. Student leftist groups said some of their members were also detained at their homes.

Turkey is not due for another presidential election until 2028, but it’s possible that Erdoğan will call an early vote to seek another term.

İmamoğlu has been confirmed as the candidate for the CHP and has performed well in recent polls against Erdoğan.

His election as mayor of Istanbul in 2019 was a major blow to Erdoğan and his party, which controlled Turkey’s largest city for 25 years.