Iran may be readying deployment of its new Russian-made S-300 missile defense system at a military facility on the outskirts of Tehran, according to new satellite images.

Heavy construction at an airbase near the Afsariyeh neighborhood in the southeast of the city suggest the location is being prepared to house the guided anti-aircraft missile system, global intelligence company Stratfor said.

Several concrete stages that will likely serve as radar detection and missile launching platforms have also been spotted.

Observers believe the base will be used to familiarize and train Iran’s military with the new system as the country upgrades from the aging S-200 shield built during the Soviet Era.

The base is located near several military facilities including Iran’s 65th Airborne Special Forces “Nowhed” Brigade as well as offices housing the IRGC’s cyber unit.

In the past, the base served as a training facility for the S-200, commonly referred to by NATO as the SA-5, but with the expanded range of the S-300 system, the base could also prove strategic to the defense of Tehran and any nuclear facilities surrounding the city.

The delivery of the missile system comes after an almost 10-year delay following the 2007 agreement between Russia and the Islamic Republic for the surface-to-air missile system.

Comparable to the U.S. Patriot missile system, Russia suspended transfer of the S-300 in 2010 following protests by the U.S. and Israel but resumed delivery after last year’s adoption of the Joint Comprehensive Plan of Action (JCPOA), or the Iran nuclear deal, aimed at curbing the country’s weapons program.

Previously, members of Congress expressed concern over Iran acquiring the S-300 system, believing the missiles would “significantly expand Iran’s defense capabilities, potentially emboldening Supreme Leader Khamenei’s pursuit of nuclear weapons.”

“Delivery of S-300 systems from Russia to Iran are still taking place and are likely not to be finished until the end of the year, so we’re likely to see more activity concerning the actual delivery or the installation of bases within Iran to host these S-300 systems,” according to analyst Sim Tack.