"The prince was taken in a helicopter for an emergency rescue in Phnom Penh", Chuon Narin told Reuters.
The former Cambodian prime minister has been seriously injured in a auto crash which killed his wife and injured at least seven others on Sunday.
Prince Norodom Ranariddh, 74, was in a convoy along with senior members of his FUNCINPEC party heading toward Sihanoukville in southwest Cambodia when a taxi traveling in the opposite direction slammed into his SUV, said a senior party member in the group.
The couple were taken to a local hospital in the Preah Sihanouk province, but Ms Phalla died a few hours later. Seven people were reported injured.
Sihanoukville police chief Gen. Chuon Narin said Prince Ranariddh, a son of the late King Norodom Sihanouk suffered head injuries.
Ranariddh was travelling from the riverside town of Kampot to Preah Sihanouk as part of campaigning for controversial national elections set for July 29.
Hun Sen, the prime minister who has been in power for 33 years, has crushed dissent leading up to the election, ensuring a resounding victory for his ruling Cambodian People's Party.
In 1997, he was overthrown as co-prime minister in a bloody coup and since his return to politics, had vowed to work with former rival and long-serving prime minister Hun Sen.
He never again reached the same level of popularity and was ejected from Funcinpec nearly a decade ago, only to return to it in 2015 after several attempted forays back into politics.
Funcinpec is taking part despite widespread complaints that the poll will be neither free nor fair after the main opposition group, the Cambodia National Rescue Party (CNRP), was banned late past year.
But he has cosied up to the former foe as part of a political comeback, and was granted one of the CNRP's parliamentary seats after they were redistributed.
In April 2015, Prince Ranariddh and his wife were also involved in a vehicle accident with a truck in Kampong Cham province's Prey Chhor district.