Saudi Arabia has detained a prominent imam and preacher at the Grand Mosque in Mecca, activists said, after he reportedly delivered a sermon criticising mixed public gatherings.

The social media advocacy group Prisoners of Conscience, which monitors and documents arrests of Saudi preachers and religious scholars, said on Sunday that Sheikh Saleh al-Talib was arrested after he delivered a sermon on the duty in Islam to speak out against evil in public.

Khaleej Online reported that in his sermon, Talib, who also serves as a judge in Mecca, derided the mixing of unrelated men and women at concerts and other mixed entertainment events.

While there was no direct criticism of the Saudi royal family in his speech, the kingdom has in recent months relaxed laws on female attendance at public events.

Saudi Arabia has yet to issue an official statement on the issue.

Hours after his reported arrest, both of al-Talib’s Engish and Arabic Twitter accounts were deactivated.

Speaking to Al Jazeera, Yahya Assiri, a UK-based Saudi human rights activist, said the kingdom’s “authorities are looking at everyone that’s influential and has a presence on the scene”.

He added: “Even those that have kept quiet or pledged allegiance to the state, even those that have been drumming up the authorities and their initiatives, even these are not safe.”

Wave of arrests

Since Mohammed bin Salman, also known as MBS, became the Saudi crown prince in June 2017, dozens of imams, women’s rights activists and members of the ruling royal family have been detained.

Among those arrested are prominent Islamic preachers Salman al-Awdah, Awad al-Qarni, Farhan al-Malki, Mostafa Hassan and Safar al-Hawali.

Al-Awdah and al-Qarni, who have millions of followers on social media, were arrested last September and accused of having links to the Muslim Brotherhood, a group Saudi Arabia blacklisted as a “terror organisation”.

Meanwhile, al-Hawali, 68, was detained after he published a 3,000-page book attacking bin Salman and the ruling family over their ties to Israel, calling it a “betrayal”.

Earlier this year, bin Salman softened the kingdom’s stance on Israel, telling the US-based Atlantic magazine that Israelis “have the right to their own land” and “there are a lot of interests we [Saudi Arabia] share with Israel.”

In March, Riyadh granted India’s national carrier permission to use its airspace to operate a direct flight between New Delhi and Tel Aviv.