Riggs National Bank Chairman Vincent C. Burke Jr. declined yesterday to reveal whether the bank has any loans to Argentina, whose ability to repay much of its international borrowings is in question because of a freeze Great Britain has placed on Argentine deposits in the United Kingdom.

But in response to a shareholder's question, Burke said the bank has been active making loans in Central and South America and does not anticipate any losses on those loans. He added that $3 million of the $15.36 million the bank has set aside to cover potential loan losses is not pinpointed for any particular problem loans the bank already knows about and is sufficient to cover any problems.

Shareholders at Riggs National Corp.'s annual meeting barely asked any questions of Burke, chairman of the company's only subsidiary, or Riggs Corp. Chairman Joe L. Allbritton.

Riggs, the District of Columbia's biggest bank, reported no increase in net income in 1981 and saw its so-called nonperforming assets more than triple to $64.3 million from $19.8 million in 1980. Nonperforming assets are loans that are not being paid on the original schedule and real estate the bank has acquired when the property owner (generally a builder) could not repay a loan. Past-due loans also jumped from $14.2 million to $39.2 million. Most of the $25 million increase was in loans to foreigners.

Allbritton, who took over Riggs last year, is trying to buy the New York Daily News, the nation's biggest general-circulation newspaper. But the former owner of The Washington Star promised shareholders that "my principal occupation is at the Riggs."

Allbritton owns television station WJLA here as well as several newspapers in New Jersey. He said his other holdings "consume practically none of my time," and said if he is successful in buying the New York News, "my modus operandi will be similar." Last year his Allbritton Communications Corp. bought the Trenton Times from The Washington Post Co.

Allbritton said that the bank is reviewing, as it has in each of the past five years, whether it wants to continue to operate its Central Charge credit-card subsidiary. Allbritton said the bank would be unlikely to move Central Charge to Delaware, as many Maryland banks have or plan to do with their Visa and Master Card operations. Delaware has no limits on the amount of interest credit card companies can charge and also permits them to charge a fee for their bank credit cards.