ANKARA (Reuters) - Turkey's military has begun deploying tanks and other armored vehicles to the town of Silopi near the Iraqi border, in a move the defense minister said on Tuesday was related to the fight against terrorism and developments across the border.

Fikri Isik said Turkey had "no obligation" to wait behind its borders and would do what was necessary if Kurdistan Workers Party (PKK) militants took a foothold in northwest Iraq's Sinjar region, around 115 km (71 miles) south of Silopi.

"We will not allow the threat to Turkey to increase," he told broadcaster A Haber in an interview.

The army deployment, disclosed by military sources, came after President Tayyip Erdogan said on Saturday that Turkey was aiming to reinforce its troops in Silopi.

Photos from the sources showed a long column of vehicles, including tanks, tank rescue vehicles and construction vehicles in single file on a dual carriageway.

The deployment coincides with an Iraqi operation to drive Islamic State from the northern Iraqi city of Mosul and after Iraqi Shi'ite militias launched a related offensive to push the jihadists out of the town of Tal Afar further west.

Erdogan said on Saturday Ankara would have a "different response" for Shi'ite militias if they "cause terror" in Tal Afar, home to a sizeable ethnic Turkmen population with historic and cultural ties to Turkey.

Sinjar, where Ankara believes the PKK is developing a presence, is situated some 50 km west of Tal Afar.

PKK

Sirnak province, where Silopi is located, is also one of the main areas of conflict between Turkey's army and the PKK, whose main bases are in the mountains of northeast Iraq.

Designated a terrorist group by Turkey, the United States and the European Union, the PKK has waged a three-decade insurgency against the Turkish state for Kurdish autonomy. More than 40,000 people have been killed in the conflict.

Largely Sunni Muslim Turkey and the Shi'ite-dominated central government in Iraq are at loggerheads about the presence of Turkish troops at Iraq's Bashiqa camp and about Ankara's demand to take part in the U.S.-backed Mosul operation.

Turkey says it has a responsibility to protect ethnic Turkmens and Sunni Arabs in the area around Mosul, once part of the Ottoman Empire. It fears both PKK militants and Shi'ite militias, which the Iraqi army has relied on in the past, will be used in the campaign and stoke ethnic bloodletting.

(Reporting by Tulay Karadeniz and Can Sezer; Writing by Daren Butler; Editing by David Dolan and Gareth Jones)