According to flood control officials, of the 11 victims three were struck by lightning and the other eight were washed away by the flood, Xinhua reported.
Vietnam's northern Lang Son province, some 130 km north of capital Hanoi and bordering China in the north, was hit the worst by the typhoon.
Approximately 5,500 Vietnamese households have been evacuated to safe places.
Typhoon Rammasun made landfall in Vietnam's northeastern Quang Ninh province's Mong Cai city, some 220 km northeast of Hanoi Saturday morning.
Rammasun, which first made landfall in eastern province of Albay in the Philippines Tuesday has claimed at least 94 lives with six still missing in that country.
In China, the toll has risen to 17 after it made landfall Friday afternoon in Guangdong and Hainan provinces, and Guangxi Zhuang Autonomous Region.