(Recasts with government statement)
By Prak Chan Thul
PHNOM PENH, Sept 3 (Reuters) - Cambodian opposition leader Kem Sokha was arrested in the capital Phnom Penh early on Sunday and the government of veteran Prime Minister Hun Sen said he was accused of treason.
The government said in a statement that it had a video clip and other evidence which pointed to "secret plans of conspiracy between Kem Sokha, others and foreigners to harm the Kingdom of Cambodia."
"The above act of this secret conspiracy is treason," the statement said.
Tension has been growing in the Southeast Asian country in the run-up to a general election next year in which the opposition party has been expected to challenge Hun Sen's rule of more than three decades.
Kem Sokha's daughter Monovithya Kem, who is also an official in his Cambodia National Rescue Party (CNRP), said on Twitter that Kem Sokha and his bodyguards had been taken away by between 100 and 200 police who did not have an arrest warrant.
"We don't know where they take him," she said. (Editing by Matthew Tostevin)