(Recasts; adds peso, bonds)
BUENOS AIRES, Aug 4 (Reuters) - Argentine stocks closed on Monday at their lowest level since November 2006, falling along with global commodities prices and amid a regional slump.
The MerVal benchmark index .MERV ended 3.78 percent lower at 1812.75 points, marking the biggest single-day drop since mid-January. It was the third straight session of losses.
"The steep fall in commodities prices didn't help at all, affecting a vast amount of shares from the start of the session. Global markets were also down," said Francisco Marra, a trader at Bull Markets Brokers.
"The selling was also encouraged by domestic factors after the president's message (on Saturday)," he added.
Brazilian and Mexican stocks closed sharply lower on Monday, and U.S. stocks fell as well.
Argentine President Cristina Fernandez gave an unprecedented press conference on Saturday, but she defended her government's actions during a four-month farm dispute and showed no sign of changing her policies or cabinet ministers.
Trade volume on the overall market was a slim $18.1 million. Of active shares, 4 rose, 55 fell and 7 were unchanged.
Food maker and grains exporter Molinos Rio de la Plata MOL.BA shed 7 percent to end at 7.55 pesos per share, while heavily weighted power firm Pampa Holding (PAM.BA) fell 6.25 percent to close at 1.5 pesos.
Meanwhile, Argentine sovereign debt fell 1.3 percent on average in over-the-counter trade, with the peso-denominated Discount bond shedding 2.8 percent amid overall risk aversion and concerns about U.S. economic health, traders said.
The peso currency firmed slightly against the dollar, although traders said they expect the central bank to try to stabilize the local currency in the range of 3.02 to 3.045 per dollar.
In formal interbank trade, where the central bank regularly intervenes, the peso firmed 0.08 percent to 3.0375/3.0400 per dollar ARS=RASL. In informal trade between foreign exchange houses, as measured by Reuters, the peso strengthened by the same percentage to end at 3.0550/3.0575 per dollar ARSB=. (Reporting by Jorge Otaola and Walter Bianchi; Writing by Hilary Burke; Editing by Leslie Adler)