BUENOS AIRES, Dec 21 (Reuters) - Argentine stocks rose on Friday for a third straight session of modest gains, influenced by an upward trend on global markets, traders said.
The MerVal index .MERV of the 25 leading stocks rose 0.23 percent to 2,145.25 points, but the index was still down 1.8 percent on the week.
"The MerVal timidly followed the strong surge in global markets, mainly because institutional investors were not trading," said Francisco Marra, an analyst at Bull Market Brokers.
Broad market volume was moderate at 110 million pesos ($35 million). Among active issues, 62 advanced, 31 declined and 11 closed flat.
Brazilian state energy company Petrobras APBR.BA closed 3.7 percent higher at 176.50 pesos a share in Buenos Aires, while index heavyweight steel-tube maker Tenaris (TENA.BA) gained 2 percent to end at 69.80 pesos.
U.S., Brazilian and Mexican stocks all traded sharply higher.
Argentine markets will be closed on Monday and Tuesday for the Christmas holidays and will reopen on Wednesday.
Government bond prices rose 0.5 percent on average in thin trade, traders said.
The biggest gainers were the Discount bond in pesos, which rose 1.2 percent, and the Boden 2014, which rose 1.3 percent <AR/BONOS>. The Par bonds denominated in dollars fell 0.6 percent.
The peso currency, which is regulated by the central bank, closed 0.16 percent weaker at 3.1400/3.1425 per dollar ARS=RASL in formal interbank trade.
In informal trade between foreign exchange houses, as measured by Reuters, the peso firmed 0.16 percent to end at 3.1525/3.1550 per dollar ARSB=. (Reporting by Walter Bianchi; Writing by Hilary Burke; Editing by Leslie Adler)