The Vanya class were a series of minesweepers built for the Soviet Navy between 1960 and 1973. The Soviet designation was Project 257.
Two ships of different hull material were constructed as trial ships for a coastal minesweeper design for the Soviet Navy that required reduced detection signatures by various naval mine types. Hull one, dubbed Project 257D was made out of wood and hull two, dubbed 257M, was constructed of low-magnetic steel. The Soviet Navy selected the wooden hull version for mass production, which featured reduced signatures for magnetic, electric, acoustic and hydrodynamic mines compared to the . By using dielectric coating and insulation, special sound dampening machinery and low-noise propellers that utilised air bubble shields to mask them, the signatures were reduced by a factor of 50 for magnetic, 8 to 10 for acoustic, 5 for electric and significant reduction for hydrodynamic mines.
Designated ("Base Minesweeper"), the ships of the initial design measured long with a beam of and a draught of . They had a standard displacement of and at full load. The minesweepers were powered by two M-870-FTK lightweight high-speed diesel engines turning two propellers creating . This gave them a maximum speed of and a maximum range of at .
These were the first minesweepers in the Soviet fleet to have hydraulic sweep equipment. They primarily mounted three types of sweeps: television hunting tow sweep, electromagnetic sweep, and contact sweep. Only one type of sweep could be used at a time. The ships were also armed a pair of twin-mounted AK-230M autocannon which had been de-magnetized and carried eight naval mines themselves. The gun was controlled by a remote Kolonka-1 ringsight director.
As the design advanced, it was found that the powerplant could handing more sweeps and an improved design with the capability of combatting magnetic-acoustic fused mines was initiated. This upgraded design, designated Project 257DM was equipped with new sweeps: loop coil/acoustic, solenoid/acoustic, and contact/acoustic. They could also operate against rising mines, a new concept coming into service by using a contact sweep paired with an acoustic sweep. Due to the design's effectiveness, they were utilized as convoy escorts in coastal waters.
In 1974, one unit was modified and had its sweep gear removed. A small mast was installed amidships, and the guns were swapped out for twin-mounted versions. The vessel was equipped with two boats for mine disposal divers.
The design underwent one further evolution, replacing the diesel engines with more powerful ones, capable of creating . This made it possible to use heavier sweeps such as barge and bottom contact sweeps. Three vessels were modernised and dubbed Project 699B, designated "Vanya-II" by NATO, were longer with a larger diesel exhaust amidships. They had a smaller displacement, registering standard and at full load. They had a range of at , carried 12 mines and were armed with a naval gun.
In total nine ships were exported to Bulgaria and Syria. All nine ships were of one design, Project 277DMF. Ships of the project were of similar construction as those of the of the other projects but had glass-reinforced plastic-sheathed hulls and measured long, with a beam of and a draught of . They had a standard displacement of and at full load. They were powered by two Type 98B diesel engines that created that gave them a maximum speed of and maximum range of at . They were armed with two /65-calibre AK-230 naval guns placed in a single mount for anti-aircraft defence. They could also carry between eight and twelve naval mines. They had Don II navigational radar and a High Pole A identification friend or foe system and a crew of 30.
Seven ships were transferred to the Bulgarian Navy in three batches during the Cold War. The first two pairs, in 1970 and 1971 respectively, coincided with a renewal of Bulgaria's postwar fleet that was prefaced by three consecutive Five-Year Plans. The final ships were acquired in 1985 during another attempt at fleet renewal, however, the poor Bulgarian economy and the breakup of the Warsaw Pact in the late 1980s saw no further acquisitions.
Syria had longstanding links with the Soviet Union during the Cold War and in December 1972, the two ships were transferred to the Syrian Navy.