TEHRAN — After suppressing the political protests that followed last year’s disputed presidential election, Iran’s security forces are now on the alert for a new kind of domestic threat — strikes and civil unrest provoked by planned cuts in fuel subsidies. Top police officials have issued a series of warnings this month against the threat of an overflow of tensions following the cuts, which some fear could set off a chain reaction of price increases and economic hardships in a country already stricken by high inflation and widespread unemployment. “The freeing up of prices has created worries in society, and this is of great importance to us,” the police chief for Tehran, Hossein Sajednia, told union and guild leaders on Thursday, insisting that security was essential for economic prosperity. The language Mr. Sajednia and other officials used echoed the warnings of sinister foreign plots the government raised when it crushed the cries of fraud and protests after President Mahmoud Ahmadinejad was re-elected in June 2009. The warnings also suggested an effort by the government to blame foreign adversaries and domestic collaborators for Iran’s economic problems.