Officials said a 240-member contingent of federal police and guards was sent to take positions in Santa Cruz provincial capital Rio Gallegos and other cities in the province after the police strikes gained momentum.
Strikers' representatives say the protest has the support of 90 percent of Argentina's police force.
The police protest is especially sensitive for Fernandez, who sees the Patagonian region as her political turf and the police action as potentially damaging to her approval ratings.
Security Minister Nilda Garre responded to Santa Cruz Gov. Daniel Peralta's requests for security reinforcements after it appeared the local law enforcement system was on breaking point because of the police strike.
Shops in many urban areas closed early or remained shut as provincial authorities told businesses they couldn't guarantee safety of their properties.
The Santa Cruz police officers are striking over a pay dispute that centers on their demand for a significant wage hike.
A provincial government offer of a 34 percent wage hike was rejected by the striking officers. The strikers want a minimum pay of $1,800 against the government offer of $1,325 per month.
Provincial government frustration with the dispute raised speculation the local authorities would declare a state of emergency but the dispatch of federal forces to the area has set aside that option, at least for now.
The police strike couldn't have come at a worse moment for the Fernandez government in Buenos Aires, which is battling soaring inflation, wage demands from other sectors and black market rates for the U.S. dollar.
Argentina is short of foreign currency and the government wants to keep its dollar reserves to honor maturing debt and to pay for imports.
In a bid to control the currency market, the Central Bank said that further dollar-peso exchange deals could only be done through banks and approved currency traders where the transactions could be monitored.
The government has also launched a concerted campaign to dissuade Argentine businesses and individuals from continuing the tradition of keeping savings in dollars.
Officials recently criticized an Argentine tendency to trade real estate in U.S. dollars.
Early in July the Central Bank banned the sale of dollars for savings. The regulator said it was suspending access to the local money exchange market for the purchase of foreign assets "with no declared specific purpose."