The tunnel, connected to some warehouses, was about 40 meters long and 1.5 meters deep. Police say PKK terrorists used the tunnel to flee from police raids as well as to attack security forces.

Police added the tunnel was also connected with the city sewer system which allowed terrorists to travel underground as far as Mount Judi.

Police uncover PKK arsenal

In another operation on two houses used as PKK terror cells in Siirt District, police uncovered an arsenal belonging to terrorist.

Siirt Governor Mustafa Tutulmaz said security units found a large amount of ammunition and arms during a search operation in two separate addresses on Thursday.

Security officials confiscated four rocket launchers, 35 anti-tank rocket nozzle, 13 anti-personnel rocket nozzle, five hand grenades, 21 Kalashnikov rifles, 51 Kalashnikov magazines, 4,568 Kalashnikov cartridges, five hand walkie-talkies, a dual band-enabled radio, 36 rocket propulsion engines, 3 Bixi heavy machine guns, 828 Bixi fireworks, 8 Bixi armor-piercing bullets, an M16 rifles, three M16 gun magazines, 302 M16 gun cartridge, a table radio, 12 grenade firing receivers, a timer, two trigger setting remote controllers, 480 hunting cartridges, one hunting pistol, 29 pistol cartridge, a pair of binoculars, first aid materials and lots of equipment for these weapons, along with digital materials and organizational documents.

The cache was displayed publicly at Siirt police headquarters.

Police also seized seven Kalashnikov rifles from another house during Thursday's operation, where a police official was martyred and seven PKK terrorists were killed.

The PKK, designated a terror group by Turkey, the US and the EU, have been fighting Turkish armed forces for nearly three decades. They renewed their armed campaign late last summer.

Security sources said police launched operations after getting a tip-off that PKK terrorists were preparing for a terror attack in house in the Ulus neighborhood of Siirt.

During the raid, terrorists opened fire on the police from inside the building. Two PKK terrorists were killed during a shootout between the police and the group.

Three security officials were taken to a hospital after being injured during the clashes. Medical sources said their injuries were not life-threatening.

Video: Video shows police raid on PKK terror cell

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in the eastern province of Siirt.

Three Kalashnikovs, ten grenades, one rocket-propelled grenade, 10 anti-tank rockets, five anti-personnel rockets and a significant amount of bomb-making materials were found in a nut orchard near the city's Police Academy.

The weapons cache was recovered along with 10 hand-held radios, 2,500 Kalashnikov cartriges, 11 cartridge clips. When discovered, most of the materials were ready to shoot and the rockets seemed to be newly-produced.

Siirt police chief Metin Özkan said the search was sparked by a tip from local residents. “This operation is a clear sign of how citizens' security has been safeguarded as a result of the recent terror operations," he told reporters.

The Turkish government launched peace talks with the PKK's jailed leader in 2012, but the process collapsed in July after a suicide bombing in Suruç. Since then, the violence flared again especially in the eastern and southeastern parts of the country.

The military has been conducting strikes against the PKK targets in northern Iraq and areas, near the border with Iraq. Officials said at least 150 members of the security forces have been killed since July while air strikes and police raids have left more than 2,000 PKK terrorists dead.

The day-long operation came after a week of killing 16 Turkish soldiers in an ambush planned by the PKK militants in the Dağlıca town of Hakkari.

According to military sources, a large number of soldiers along with military helicopters conducted anti-PKK operations in rural areas between Tunceli, Ovacık, Pülümür and Erzincan. The operations continue in several mountainous areas of Hakkari, Van and Siirt.

Seventeen PKK militants have been killed in operations in an area between Tunceli and Erzincan, while 5 others were killed in Hakkari.

In a related operation, the Turkish army killed 6 terrorists in the Eruh district of Siirt and 3 others in the Pervari district.

Another PKK member has been killed in the eastern province of Van.

Operations are still continuing, sources said.

Police detain 22 PKK suspects in Şanlıurfa

Meanwhile, scores of PKK militants have been detained in the Viranşehir district of the border province of Şanlıurfa.

After receiving a tip-off that a group of terrorists were scheming to launch a bomb attack in the city, the Şanlıurfa Police Department launched an operation in a park of Viranşehir and detained two terrorists while they were planning to place a bomb there.

Police units then widened the raid by conducting search operations in 35 addresses and arrested 20 PKK suspects. Police identified that five among the detainees had organized several bomb attacks on police vehicles in the district.

Meanwhile, a total of 4 other Turkish soldiers were killed in the southeastern Turkish province of Diyarbakır during the two-day clashes between the PKK and Turkish security forces.

The PKK, which is considered a terrorist group by Turkey and much of the international community, including the United States and the European Union, has been involved in a separatist struggle with Turkey since the early 1980s.

Turkey blames the group for the deaths of thousands of people.