Suburban Bancorporation reported a modest increase in second-quarter operating profits yesterday, while D.C. National Bank posted an increase of 15 percent in earnings for the same period.

Not counting gains or losses from securities transactions, Hyattsville-based Suburban reported earnings of $4.4 million (93 cents a share) compared with $4.3 million (90 cents) a year earlier. The company owns Suburban Trust Co., the largest bank in suburban Maryland.

First-half operating earnings were $8.6 million ($1.81) compared with $8.2 million ($1.74), for a return on stockholders' equity in the banking business of more than 15 percent.

Suburban reported losses on selling securities of $326,000 in the first half and $197,000 in the second quarter. As a result, second-quarter net income was flat at $4.25 million (90 cents) in both periods. A statement attributed the securities sales to a decision by management to sell low-yielding investment securities and replace them with similar securities with higher interest returns to improve future profitability.

Deposits rose $64 million from a year earlier to $1.29 billion on June 30, while loan volume declined $48 million to $819 million.

D.C. National's second-quarter earnings from operations were $548,000 ($2.60 a share) compared with $476,000 ($2.32) last year. First-half operating profits rose to $1.14 million ($5.40) from $838,000 ($4.09). Assets of the District's seventh-largest bank on June 30 were $161 million.