PARIS (REUTER) - Car bombings have claimed at least 50 lives in a week in and around Algiers and plunged the city into fear as Islamist guerrillas step up their insurgency. Two car bombs killed at least three people and wounded scores in the garrison city of Blida 50 km (30 miles) south of Algiers on Wednesday, residents said by telephone. The day before, two car bomb explosions killed at least 12 and wounded scores in Algiers. Newspapers said those bombs raised the toll since the start of the Moslem holy month of Ramadan on January 10 to at least 150 dead and 170 wounded. No one has claimed responsibility but analysts believe the bombs are a message to President Liamine Zeroual that the Islamic fundamentalists remain a formidable force despite repeated claims that the government has crushed them. Algeria's radical Armed Islamic Group (GIA) had promised to intensify its "holy war" during Ramadan, threatening a 50-bomb campaign. Some Algiers residents said their crowded city of nearly four million was experiencing the worst wave of bombings since the Ramadan 1962, when hardline French colonialists unleashed a campaign of violence to oppose Algeria's independence. The authorities, conceding they cannot stop the car bomb onslaught, appealed for public help to halt the guerrillas. Interior Minister Mustpaha Ben Mansour said: "It is difficult to ward off bomb attacks but with the population's collaboration and vigilance, terrorism will be defeated."