KHARTOUM: A high-ranking member of a leading Sudanese opposition party has been detained, the party said on Sunday, after the opposition vowed to step up anti-regime protests.

Kamal Omar, head of the politbureau in the Popular Congress Party, was taken from his home on Saturday by suspected agents of the National Intelligence and Security Service, said Bashir Adam Rahma, the party's foreign relations secretary.

"They asked him to take his bag and to take some clothes. That means he is going to stay for a while," Rahma told AFP.

Popular Congress is led by the Islamist Hassan al-Turabi, a former mentor turned critic of President Omar al-Bashir.

Rahma said Kamal Omar was to fly to Qatar on Monday for an appearance on Al-Jazeera satellite news channel.

"Probably they don't want him to participate in that well-watched programme," Rahma speculated.

Demonstrations, sparked by high inflation, have continued in Sudan for an unprecedented three weeks and have been met by what the European Union called a "a violent crackdown."

The EU and Canada have also expressed concern at the detention of journalists and political activists.

Last week the Popular Congress and about 16 other opposition parties signed a charter pledging to mobilise their members for peaceful protests aiming to topple the ruling National Congress Party (NCP) Islamist regime.

"There is no hope that there will be constitutional reform," Rahma said. "With the wind of the Arabic Spring, now the civil unrest could be the safest way to bring democracy and peace to Sudan again."

Activists, however, have dismissed the political opposition as weak.

The NCP's political secretary, Hasabo Mohammed Abdel Rahman, on Thursday said his party remained committed to dialogue "with all political forces," the official SUNA news agency said.

President Bashir has played down the demonstrations as small-scale and not comparable to the Arab Spring uprisings in Egypt and elsewhere, maintaining that he himself remains popular after 23 years in power.

Sudan has lost billions of dollars in oil receipts since South Sudan gained independence on July 9 last year, taking with it about 75 percent of Sudanese crude production.

The north has been left struggling for revenue, plagued by inflation which reached 30.4 percent in May, and with a severe shortage of dollars to pay for imports.