Sudanese authorities have fired tear gas at protesters near the country's capital as demonstrations continue.

Hundreds of people were fired on outside a mosque in Omdurman after activists called for protests to take place after Friday prayers.

Demonstrations have also erupted in areas of north Khartoum, Sudan's capital, according to AFP.

It comes after Sudanese authorities were accused of arresting nine opposition activists, Reuters reports.

At least 19 people have died during nine days of anti-government protests, according to official figures.

Amnesty International said on Tuesday it believed that 37 protesters had been shot dead.

In a joint statement reported by Reuters, several groups involved in the protests said nine opposition leaders had been arrested in Khartoum. The individuals reportedly include Siddiq Youssef, a senior leader of Sudan's Communist Party, and leaders from the pan-Arab Ba'ath and Nasserist parties.

A spokesperson for Sudan's intelligence agency - the National Intelligence and Security Service - denied any knowledge of the arrests, Reuters reports.

Protests first erupted earlier this month after bread and fuel price rises were announced.

But they have escalated into broader calls for an end to the 29-year rule of President Omar al-Bashir. Activists accuse him of mismanaging the economy.

Over the past year, the cost of some goods has more than doubled, while the Sudanese pound has plunged in value.

Three-quarters of Sudan's oil wealth has also been lost after the country's southern half voted to secede in 2011, leading to the formation of South Sudan.

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