* Riot police deploy following riots
* Cost of flour, oil has doubled
By Lamine Chikhi
ALGIERS, Jan 7 (Reuters) - Anti-riot police deployed in the main arteries and around some mosques of Algiers ahead of Friday prayers after street riots this week over food price rises and the lack of job opportunities.
Hundreds of youths clashed with police in several Algerian cities earlier in the week, and ransacked stores in the capital.
On Wednesday, riot police used tear gas to disperse youths in the Algiers neighbourhood of Bab el-Oued, where the most violent of the protests occurred.
OPEC-member Algeria has seen periodic outbreaks of social unrest but riots due to rises in the cost of basic foods are rare.
The cost of flour and salad oil has doubled in the past few months, reaching record highs, and 1 kg of sugar, which a few months ago cost 70 dinars (27 U.S. cents), is now 150 dinars.
On Friday, riot police carrying tear gas rifles and batons maintained a strong presence around Algiers' main mosques and streets, a Reuters reporter said.
In the popular Belcourt district, dozen of trucks carrying the anti-riot force were parked.
"There is a bit of tension in the air," said Salim Hanachi on his way to Belcourt's mosque. "We hope it will go well".
Officially unemployment is about 10 percent in Algeria, but independent organisations put it closer to 25 percent.
The government has announced an investment plan worth $286 billion over the next four years to create jobs and improve living conditions. President Abdelaziz Bouteflika has also promised 1 million new housing units by 2014.
In Tunisia, students, professionals and youths have in recent days mounted a series of protests over a shortage of jobs and restrictions on public freedoms.
The protests against Tunisian President Zine al-Abidine Ben Ali's rule have shaken the North African nation. (Reporting by Lamine Chikhi; Editing by Giles Elgood)