Anger over high food and fuel costs has spawned a rash of violent unrest across the globe in the past six months.

From the deserts of Mauritania to steamy Mozambique on Africa's Indian Ocean coast, people have taken to the streets. There have been "tortilla riots" in Mexico, villagers have clashed with police in eastern India and hundreds of Muslims have marched for lower food prices in Indonesia.

Governments have introduced price controls and export caps or cut custom duties to appease the people who vote for them, but on streets across Africa, those voters want them to do more.

Sub-Saharan Africa is particularly vulnerable: most people survive on less than $2 a day in countries prone to droughts and floods where agricultural processes are still often rudimentary.

For African households, even a small rise in the price of food can be devastating when meals are a family's main expense.

"People have been driven to destruction because they no longer know what to do or who to talk to," said Ousmane Sanou, a trader in Patte d'Oie, one of the areas worst hit by February riots in Burkina Faso's capital, Ouagadougou.

"They understand it's the only way to get the government to change things. Prices must come down -- otherwise we're heading for a catastrophe."

Over 300 people were arrested in some of the worst violence for years in normally calm, landlocked Burkina, prompting the government to suspend custom duties on staple food imports for three months -- measures some other countries have also taken.

But unions have threatened to call a general strike in April unless prices fall further.

Anger over rising prices also fuelled violence in Mauritania late last year. And at least six people were killed when taxi drivers in Mozambique rioted over fuel prices in February.

In Senegal, police raided a private television station last Sunday after it repeatedly transmitted images of police beating demonstrators with electrified batons and firing tear gas during an illegal protest over high food prices in the capital Dakar.

The poor country on Africa's west coast witnessed the worst rioting in more than a decade last year, as hundreds of youths smashed windows and burned tyres in anger at high prices and government efforts to clear away street traders.

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The UN World Food Programme (WFP) says staple food prices in some parts of Africa have risen by 40 percent or more in six months. And this on a continent where malnutrition rates in some areas regularly top emergency levels even in an average year.

Food inflation in Africa is 2.8 percentage points higher than headline inflation, the International Monetary Fund (IMF) said this month.

In South Africa last week, central bank Governor Tito Mboweni warned consumers to "tighten their belts" as the targeted inflation measure reached a five-year high at 9.4 percent year-on-year in February, from 8.8 percent in January.

Already, consumer spending has slowed sharply, and confidence levels are at multi-year lows -- all this on top of chronic energy shortages in Africa's biggest economy.

In Cameroon, a taxi drivers' strike over rising fuel costs -- caused by many of the same factors pumping up food prices -- triggered widespread rioting exacerbated by anger over the cost of food, high unemployment and plans by President Paul Biya to change the constitution to extend his 25-year rule.

Government ministers said around 25 to 40 people were killed, although a human rights group put the toll at over 100.