The two sides were scheduled to meet for a sixth round of negotiations on Sunday. Oman, which was set to host the talks, said on Saturday that this round had been canceled.

Maj. Gen. Mohammad Bagheri, the chief of staff of Iran’s armed forces, was among the dead, according to Iranian state media. Officials said a top nuclear negotiator was also killed.

The two powers have been exchanging barrages since Israel attacked Iran and killed many of the country’s top military leaders and scientists.