Sudanese security agents on Wednesday arrested four prominent leftist opposition figures, their alliance said, as authorities press a bid to crush protests sparked by fuel price hikes.

The National Intelligence and Security Service has seized several opposition politicians in the past few weeks as part of the crackdown to prevent street protests as seen during deadly demonstrations in 2013.

NISS arrested top leftist leaders Siddig Yousif, Tareq Abdelmajid, Mohamed Diaelddin and Munzier Abumali at its Khartoum office where they had been summoned on Wednesday, said the National Consensus Forces alliance.

Family members of Yousif and Abumali confirmed their arrests to AFP.

Sudan's opposition groups including the Communist Party, a member of the National Consensus Forces, had called for street protests against President Omar al-Bashir's government after the authorities hiked prices of petrol and diesel by about 30 percent this month.

Groups of protesters have staged small rallies in parts of Khartoum and some other towns since then, but they were quickly dispersed by anti-riot police.

Several protesters including women have been put on trial for staging rallies in the capital.

Similar fuel subsidy cuts triggered the deadly unrest of 2013 which drew widespread international criticism.

Rights groups say about 200 people were killed in that crackdown, but the government puts the death toll at less than 100.

The government has been forced to progressively reduce fuel subsidies since 2011 when South Sudan seceded and took with it nearly three-quarters of the formerly united country's oil reserves.

Government officials and leaders of the ruling National Congress Party were not immediately available for comment on the latest arrests.