The United States has formally complained to China after alleging that the Chinese military injured two U.S. airmen by directing high-grade lasers at American aircraft in Djibouti. Pentagon spokeswoman Dana W. White said at a briefing on Thursday that the United States has requested China investigate multiple incidents in recent weeks in which U.S. aircraft in Djibouti have been affected by unauthorized Chinese laser activity. White said the Pentagon was confident that Chinese nationals were responsible. She said there had been more than two but fewer than 10 such incidents, which she said had increased in frequency in recent weeks. “It’s a serious matter,” White said. “And we’re taking it very seriously.”