Under the 2004 agreement, Russia is to hand over to China the Tarabarov and about half of the Bolshoi Ussuriysky islands (around 375 sq km or 145 sq miles) located at the junction of the Amur and the Ussuri rivers and close to a major Russian city, Khabarovsk.
General Valery Putov, head of the Federal Security Service's (FSB) Far East department, said the demarcation of the border section had been completed.
"Frontier checkpoints on the islands have been moved to a different location, where border guards will relocate in August," Putov said. "And a 10-km section of the border near Khabarovsk has been equipped with alarm systems, video surveillance cameras and thermal imaging devices."
The two islands - occupied by the Soviet Union in 1929 and referred to collectively in Chinese as the Heixiazi - were the site of several military skirmishes during the 1960s.
The 2004 agreement on the eastern sector of the 4,300-kilometer border, the world's longest land frontier, was signed after China agreed to drop territorial claims to the other islands around Khabarovsk. The deal put an end to a decades-long territorial dispute between the two states.
Russia and China signed border agreements in 1991 and 1994 delimiting the eastern and western sections of their frontier, but several minor sectors were left unresolved.
The agreement has not met complete support in both countries. Nationalists in Russia rallied against "ceding Russian territory," while commentators in Hong Kong and Taiwan criticized the document as sealing the loss of former Chinese territory.
Concerns were also raised in Russia about the proximity of the Chinese border to Khabarovsk. Russian officials said there was no military threat from the country.
