July 21 (Reuters) - Trading platform Interactive Brokers IBKR.O reported a 35% rise in second-quarter profit on Tuesday, bolstered by elevated trading activity due to a sharp rally in U.S. equity markets during the period.

The S&P 500 .SPX and Nasdaq posted strong gains during the April-to-June quarter as investors looked past geopolitical uncertainty and remained optimistic about AI-driven earnings growth.

Here are some more details:

• The broker's net interest income rose 23% to $1.06 billion in the second quarter, as a result of higher average customer margin loans and credit balances.

• Commission revenue - the amount the brokerage earns when clients execute trades - increased 30% in the reported quarter compared to the prior year supported by higher customer trading volumes across major asset classes, including equities, futures and options.

• Daily average revenue trades, or DARTs, which signify the average trades per day generating commissions or fees, rose 36% in the quarter to 4.82 million trades.

• The Greenwich, Connecticut-based company reported net income available for common stockholders of $312 million, or 69 cents per share, for the three months ended June 30, compared with $224 million, or 51 cents per share, for the same period, in the prior year.

• Peer brokerage firm Charles Schwab SCHW.N also posted a record second-quarter profit, boosted by robust trading activity and increased asset management fees.