MOSCOW, February 4. /TASS/. An appellate court in Moscow has prolonged the term of arrest for US citizen Paul Whelan until March 29. The defendant is in Russian custody on espionage charges, TASS reports.

"The defense’s appeal over the extension of the arrest as a pre-trial restriction is not accepted, the ruling of the court of first instance remains unchanged," the judge declared in the verdict. The motion was considered behind closed doors, since confidential materials are involved in the case.

Whelan’s defense team plans to familiarize themselves with the materials of the case within a week, after which it can be turned over to the court, lawyer Vladimir Zherebenkov told TASS.

"Next week, we are planning to finish work on studying the materials of the case," he said.

US citizen Paul Whelan, 48, who also holds British, Canadian and Irish citizenship, is a global security chief at BorgWarner, a Michigan-based automotive components company. The Russian Federal Security Service (FSB) said Whelan was detained on December 28, 2018 in Moscow while on an alleged spy mission. A criminal investigation was launched against him on espionage charges carrying a penalty of anywhere from 10 to 20 years behind bars.