* Turkish jets, special forces involved in raid

* Ankara vowed to cleanse Islamic State from border

* Turkey worried about influence of Syrian Kurdish YPG

(Adds more details from operation, bylines)

By Humeyra Pamuk and Orhan Coskun

ISTANBUL/ANKARA, Aug 24 (Reuters) - Turkish special forces units and jets supported by warplanes from the U.S.-led coalition launched an operation in northern Syria to wipe out Islamic State militants along the Turkey-Syria border, Turkish officials said.

The Turkish army began firing artillery rounds into the Syrian border town of Jarablus at around 0100 GMT and Turkish and U.S. warplanes pounded Islamic State targets with airstrikes as part of the operation, Turkish military sources said.

White and grey plumes of smoke rose from atop hills in northern Syria, Turkey's CNN Turk television showed, in footage broadcast live from the Turkish town of Karkamis across the border from Jarablus. The boom of artillery fire was audible.

Turkish military sources said a ground incursion has yet to start, but a group of Turkish special forces had entered Syria while Turkish and U.S.-led coalition jets hit four Islamic State targets and Turkish artillery struck more than 60 targets.

"The aim of the operation is to ensure border security and Syria's territorial integrity while supporting the U.S.-led coalition against Islamic State," one military source said, adding work to open a passage for ground forces was underway.

Turkey had vowed on Monday to "completely cleanse" Islamic State militants from its border region after a suicide bomber suspected of links to the group killed 54 people at a Kurdish wedding in southeastern city of Gaziantep.

Turkey is also concerned about the growing influence of Syrian Kurdish militant groups along its border, where they have captured large areas of territory since the start of the Syrian war in 2011. Ankara sees them as tied to the Kurdish militants fighting an insurgency in Turkey.

At least nine mortar shells from Jarablus had landed into Turkish border town of Karkamis and nearby on Tuesday, forcing many residents to flee the town, a Reuters witness said.

The Syria operation also came as Syrian rebels backed by Turkey had said they were in the final stages of preparing an assault from Turkish territory on Jarablus, aiming to preempt a potential attempt by Syrian Kurdish YPG militia to take it.



PRE-EMPTING KURDISH FORCES

The Kurdish YPG militia, a critical part of the U.S.-backed campaign against Islamic State, took near complete control of Hasaka city on Tuesday. The group already controls swathes of northern Syria where Kurdish groups have established de facto autonomy since the start of the Syria war.

Their growing influence has alarmed Ankara, which is fighting its own insurgency with militants from the outlawed Kurdistan Workers Party or PKK, who officials blame for an escalation of attacks in the southeast of Turkey.

Ankara is focused on preventing the YPG or its allies building on recent advances against Islamic State by capturing Jarablus. The U.S.-backed Syria Democratic Forces alliance (SDF), including the YPG, captured the city of Manbij, just south of Jarablus, from Islamic State earlier this month.

Turkey is still in shock after a failed July coup by rogue solders who tried to overthrow President Tayyip Erdogan and the government, killing 240 people and triggering a purge of suspected coup supporters in the army and civil service.

Angered by a perceived lack of Western sympathy over the coup, Turkey has chilled ties with Washington and the European Union while ending a diplomatic row with Russia and proposing more military cooperation with Moscow in fighting Islamic State in Syria.

Those growing ties between Ankara and Moscow are worrying Turkey's Western allies.

Turkish Deputy Prime Minister Numan Kurtulmus said this week that northern Syria should not become the domain of one group and that a "secure zone", an internationally policed buffer area Turkey proposed in vain in the past, should be reconsidered.

A Syrian rebel with one of the Turkey-backed groups said the fighters were waiting for the signal to enter Jarablus and a second rebel said around 1,500 fighters were now gathered at a location in Turkey to take part.

(Writing by Patrick Markey; Editing by Kim Coghill) ((humeyra.pamuk@thomsonreuters.com; +90 212 3507062; Reuters Messaging: humeyra.pamuk.reuters.com@reuters.net))