Protests in Sudan are in their second week in response to the government's decision to install austerity measures to address a looming economic crisis.
The government's oil-dependent economy has suffered since South Sudan's independence last year. Sudan controls oil export routes though South Sudan has authority over most of the oil fields.
The Sudanese currency has since lost value as the rate of inflation in May topped 30 percent.
Sudan President Bashir al-Assad was quoted by the independent Sudan Tribune as saying he would send in "mujahedin" to address growing frustration by demonstrators.
British Foreign Office Minister for Africa Henry Bellingham said he was increasingly concerned by Khartoum's reaction to the protests.
"I call for the immediate release of those detained while engaged in peaceful protest, and for the security forces to act with restraint and avoid the use of force in responding to peaceful demonstrations," Bellingham said in a statement.