The health of the Kuwait's 91-year old emir has shown "significant improvement", parliament quoted the prime minister as saying in a tweet on Tuesday.

"There is a significant improvement, thank God," Prime Minister Sheikh Sabah Al-Khalid Al-Sabah was quoted as saying.

Emir Sheikh Sabah al-Ahmad al-Sabah is in the United States completing medical treatment following surgery for an unspecified condition in Kuwait.