Fuel price hikes that sparked deadly protests in Sudan were designed to prevent economic meltdown, President Omar al-Bashir said Tuesday in his first comments on the unrest.

"The latest economic measures aim at preventing the collapse of the economy following the increase in inflation and instability in the exchange rate," the official SUNA news agency quoted him as saying.

Bashir also spoke of "conspiracies being planted by the saboteurs against our country."

On September 23 the government cut petrol subsidies, driving up pump prices by more than 60 percent.

The move was part of measures designed to stabilise an economy plagued by inflation and a weakening currency since South Sudan separated in 2011, taking with it most of Sudan's oil production.

The lost oil accounted for the majority of Khartoum's export earnings, costing the country billions of dollars. Reducing subsidies on petroleum will save billions, the government says.

Bashir said the economy has suffered "negative impact" from the separation of the South and the disappearance of oil revenue.

But the public struggled to understand why their "brothers and daughters" had been shot dead during protests.

"Peaceful demonstration is a civic right," Bashir said, while SUNA added that he "asked God to have mercy upon the martyrs".

Yusif Mohammed, 50, a teacher whose brother was killed in Khartoum's twin city of Omdurman, said "we are very angry about what happened because those protesters, their only weapons were stones and their shouts.

"Why were they gunned down?"

Osama Mohammed, 47, who works in a private company, told AFP: "After the deaths of those youths we will not keep silent."

Inflation rose to more than 40 percent earlier this year but fell to 22.9 percent by August, according to official data.

Such figures do not appear to correlate with local market prices, which have continued to rise.

Last week's unrest sent the Sudanese pound even lower, to around eight pounds to the dollar.

On the widely used black market, the pound has now lost about 50 percent of its value over the past two years.

Authorities say 34 people have died since petrol and diesel prices jumped, sending thousands into the streets in the worst urban unrest during Bashir's 24-year rule.

He took power in a 1989 Islamist-backed coup.

'Spilled blood to fuel more protests'

The real death toll was difficult to determine but "could be as much as 200," a foreign diplomat has told AFP.

"Our neighbour was killed in a demonstration. After what happened, we have lost confidence in this government," said Sosan Bashir, 35, a civil servant who lives in North Khartoum.

"Why did they kill our brothers and daughters?"

Their spilled blood will fuel more protests "to overthrow this regime," she predicted.

Small-scale demonstrations did continue in the Khartoum area.

About 100 female students demonstrated at Ahfad University for Women, the university president said, while a crowd rallied for the fourth straight day in memory of Salah Sanhouri, 28, a pharmacist gunned down during a protest last Friday.

More than 30 vehicles, mostly from the state security bureau's military wing, surrounded the headquarters of Umma, a main opposition party, on Tuesday night an AFP reporter said.

The unusual security presence occurred as party leader Sadiq al-Mahdi addressed about 1,000 of his followers inside.

Small opposition parties also reported encounters with security personnel. Senior members of the Sudanese Congress Party said their president Ibrahim Elsheikh had been arrested.

Congress belongs to an opposition alliance seeking a peaceful end to Bashir's regime. The alliance said three officials of the Baath and Communist parties had also been rounded up.

Protesters have echoed calls for the downfall of the regime made during the 2011 Arab Spring revolts, which toppled longtime rulers in Tunisia, Egypt, Libya and Yemen.

Bashir saluted "the role being played by the people to foil the conspiracies being planted by the saboteurs against our country," SUNA said.

On Monday Interior Minister Ibrahim Mahmoud Hamed blamed "overseas foundations" for supporting unrest last week.

The government says it has arrested hundreds of "criminals" and had to intervene last week when crowds turned violent, attacking petrol stations and police facilities.

But Ahmad Omer, 44, said one of his relatives -- shot dead during a demonstration -- was not the type to destroy public property.

"Why did the government shoot them? Or if the government didn't shoot them, it has to bring to justice those responsible," he said.