OMDURMAN, Sudan (Reuters) - Dozens of protesters chanted anti-government slogans as they left Friday prayers at a major mosque near Sudan’s capital, a day after a prominent figure in President Omar al-Bashir’s party called for him to resign.

Security forces fired teargas to break up the crowd in Omdurman, as demonstrations against price rises, cash shortages and other economic hardships stretched into their third week.

A group of unions that has organized the protests said one of its leaders, Mohammad Naji al-Assam, was arrested at noon, without giving more details.

“The association condemns arbitrary detentions, which will not stop it from continuing the march with the people for the sake of freedom and change,” the Sudanese Association of Professionals said on Twitter.

The protests are the most persistent opposition Bashir has faced since he took power in an Islamist-backed coup nearly 30 years ago.

Bashir and the head of Sudan’s National Intelligence and Security Service have called for restraint in the response to the protests, which government officials have blamed on unnamed infiltrators.

Friday’s protesters, mainly young men, chanted “peaceful, peaceful” and “fall, fall,” as they called for a change in government outside Al-Sayed Abd al-Rahman al-Mahdi mosque, which has ties to the opposition Umma party.

Their march was much smaller than ones that have broken out in cities across Sudan since Dec. 19. Organizers have urged people to march again toward the presidential palace in Khartoum on Sunday.

RECORDING

Al-Shafi’ Ahmad Mohammad, the first secretary-general of Bashir’s National Congress Party, issued a rare call on Thursday for Bashir to step down. In a voice recording circulating on WhatsApp, he identified himself and said that Bashir should resign and form a transitional government “to save the country”.

There was no reaction to his message from the government and he did not immediately respond to a call to ask for further comment.

Mohammad’s call came after opposition parties said on Tuesday they wanted Bashir to dissolve the government and form a transitional administration that would set a date for elections.

Their petition also called for the investigation of alleged abuses by security forces during recent demonstrations across Sudan.

Authorities have said 19 people, including two security officials, have died during the demonstrations. Amnesty International said last week it had credible reports that 37 protesters had been killed by bullets fired by security forces.

Barraq al-Nathir al-Warraq, a human rights activist in Sudan, said Sudanese security forces have detained around 2,000 people since the beginning of the protests. Those detained include political activists, journalists and civil society members.

Sudan’s economy has struggled to recover from the loss of three quarters of its oil output - its main source of foreign currency - since South Sudan seceded in 2011, keeping most of the oilfields.

The United States lifted 20-year-old trade sanctions on Sudan in October 2017. But many investors have continued to shun a country still listed by Washington as a state sponsor of terrorism, whose president is wanted by the International Criminal Court over charges of masterminding genocide in Darfur - charges he dismisses.