Russia’s Severnaya Verf shipyard in St. Petersburg has signed a contract on the overhaul of two warships for the Algerian navy, the company’s press service said on Thursday.

The Russian shipbuilder will modernize a Nanuchka II class corvette and a Koni II class frigate, which have been in service with the Algerian navy since the 1980s.

“The contract has been signed in the framework of an agreement between [Russian state-run arms exporter] Rosoboronexport and the Algerian Defense Ministry,” the company said in a statement.

The agreement, inked in 2007, envisioned the overhaul of three warships of each class. Russia delivered the first pair, consisting of a Nanushka II class corvette and a Koni II class frigate, to Algeria in February, 2011.

About 80% of onboard systems were replaced in the course of repairs, and the ships' service life was extended for 10 years.

The second pair of warships is being modernized at Severnaya Verf under a 2008 contract.

“The vessels will sail for sea trials in June, and will be delivered to the customer in July,” the company said.

Algeria is a key buyer of Russian weaponry. According to the Russian Federal Service for Military-Technical Cooperation, sales of military equipment to Algeria currently constitute 15% of Russia’s arms exports.