Sudan security forces have arrested 14 professors who were gathering to protest outside Khartoum University on Tuesday, witnesses said, as anti-government demonstrations neared the end of their eighth week.

Doctors also demonstrated outside state and private hospitals in Sudan’s capital and other cities against the rule of President Omar al-Bashir, witnesses added.

Union members, students, opposition activists and others, frustrated with economic hardships, have held near daily protests since Dec. 19, in the most sustained challenge to Bashir’s three decades in power.

Photos posted online on Tuesday showed people holding banners marked with “Freedom, justice and peace”, “No to torturing and killing protesters” and other slogans.

Rights groups say at least 45 people have been killed in the protests since they began on Dec. 19, while the government puts the death toll at 31.

Bashir has blamed the unrest on unidentified foreign powers and showed no signs of bowing to demands to quit.

But he and some senior officials have adopted a more conciliatory tone in recent weeks and promised to free detained protesters.