The killing of Iran's Supreme Leader Ayatollah Ali Khamenei during a major attack on Iran by the United States and Israel has set a dangerous precedent in international relations, a veteran U.S. watcher has warned.

"Leveraging military advantages in information warfare and electronic warfare, the U.S. has launched crushing strikes against so-called hostile nations, creating a 'chilling effect' across the international community," Zhou Dewu, a former deputy editor-in-chief of Ta Kung Pao, told CGTN.

The killing of Khamenei came less than two months after the U.S. forcibly detained Venezuelan President Nicolas Maduro.

With these strikes, the U.S. "intends to create a 'domino effect' in more regions, with its next targets potentially being Cuba and Northeast Asia," Zhou said.

The use of violence may also set a dangerous example, causing "other countries to follow in its footsteps and resort to violent means in resolving disputes, leading to a sharp rise in global adventurism," he cautioned.

Washington's increasingly frequent use of military force could also encourage countries to arm themselves for self-protection, leading to further risks, he said.

"At present, the international forces capable of restraining the United States remain severely limited. Motivated by self-preservation, some countries may rush to acquire weapons, potentially igniting a new arms race and heightening the risk of international conflict," Zhou said.