The number of protesters killed in Sudan has risen to 24 since demonstrations began last month, according to the head of the country's fact-finding committee, even as rights groups state a much higher toll.

According to Human Rights Watch, at least 40 people have been killed in clashes during the anti-government demonstrations.

People took to the street on December 19 after the government tripled the price of bread. Since then, tensions have escalated into nationwide rallies, with protesters calling for President Omar al-Bashir's resignation.

In response to the demonstrations, riot police and security agents have broken up the rallies by firing live ammunition and volleys of tear gas, rights groups reported.

Al Jazeera's Hiba Morgan, reporting from Khartoum, said last week bullets were fired at a hospital in Omdurman, Sudan's second largest city, targeting patients and doctors.

Al-Bashir, who has been ruling the country since a military coup in 1989 and remains wanted by the International Court of Justice for war crimes, has blamed the protests against his government on "conspirators".

In a joint statement on Tuesday last week, the United States, Norway, Canada and the United Kingdom condemned the violence and said Sudan's "actions and decisions over the coming weeks will have an impact on the engagement of our governments and others in the coming months and years", referring to ongoing efforts by the US and the UK to normalise relations with Sudan.

Although the immediate trigger for the protests was the increase in the price of bread, Sudan has been facing a mounting economic crisis over the past year, partially caused by an acute shortage of foreign currency.

Repeated shortages of food and fuel have been reported in several cities, including the capital, Khartoum, while the cost of food and medicine has more than doubled.

Al-Bashir and other officials have blamed Washington for Sudan's economic woes, as it had imposed a trade embargo on Sudan in 1997 that was lifted only in October 2017.

The president has remained defiant, telling thousands of loyalists at a Khartoum rally on Wednesday that his government would not give in to economic pressure.

"Those who tried to destroy Sudan... put conditions on us to solve our problems, I tell them that our dignity is more than the price of dollars," al-Bashir said.

Across the Nile in Khartoum's twin city of Omdurman, three demonstrators were killed on Wednesday as police fired tear gas to disperse the protest, the authorities said.

Al Jazeera's Morgan said that there were concerns among the protesters that the government would escalate its use of force in an attempt to put down the protests.

"People are saying that the force used against them by the government is brutal and that it increases day by day," Morgan said.

Human rights groups say more than 1,000 people, including opposition leaders, activists journalists and demonstrators, have been arrested since the protests began.