Helsinki’s main stock index rose to its highest level in more than 25 years on Tuesday as investors responded to signs of easing tensions between the United States and Iran. The OMXH general index closed at 13,463.83 points, up about 0.5 percent on the day. The level marked its highest closing figure since 2000, according to local market data. The rise followed a broader trend across global markets, where investors reacted to reports that Washington and Tehran could return to negotiations.