The lawyer for the most senior Russian official to face charges in two decades says his client was illegally detained while leaving the office of state-owned oil company Rosneft and held by a security agency for six hours.

Economic Development Minister Alexei Ulyukayev was detained earlier last month after he allegedly accepted a $2 million bribe from state oil company Rosneft in a sting set up by the FSB domestic security agency. The investigators did not reveal the details of the operation, fueling speculation that Ulyukayev was set up.

Ulyukayev's lawyer told the court Monday the FSB stopped Ulyukayev's car as he was leaving Rosneft's headquarters, took his phone and kept him in de facto custody for six hours until 11:30 p.m. when he was officially named as a suspect.