Photograph: Google maps

Multiple cross-border attacks - by Turkey, Islamic State forces and others - along the line dividing Syria from Turkey were reported Tuesday, just a day ahead of a planned visit to Ankara by US Vice President Joe Biden.

Turkey started shelling Islamic State positions over the border on Monday evening and also, separately, attacked Kurdish forces further south inside Syria, the state-run Anadolu news agency reported.

The Kurds, backed by the US, are locked in battles with Islamic State, but are also targeted by Turkish forces, which fear they could back an uprising by Kurds living within Turkey.

The shelling of Islamic State in Jarablus, a city on the border, also continued for a second day. The extremist group retaliated with mortar fire into Turkey, landing in Karkamis, a small town which Turkish police were evacuating out of concern for resident's safety.

Also, three rockets fired from Syria landed Tuesday in Kilis, southern Turkey, about 80 kilometres away.

There were other signs Turkey was intensifying the fight against Islamic State.

Non-Kurdish Syrian rebel factions have said Turkey plans to utilize them to attack Islamic State in Jarablus. Turkish Foreign Minister Mevlut Cavusoglu said Ankara would lend "all manner" of support to an operation there, broadcaster NTV reported, without specifying further.

Cavusoglu has pledged to "cleanse" the extremists from its border and also said Turkey will fight against the Kurdish People's Protection Units (YPG), the US-backed force in Syria. Prime Minister Binali Yildirim on Saturday said Turkey will be more active in Syria.

A rebel fighter told dpa the operation had begun by moving fighters from north-western Syria, though Turkey, towards Jarablus, but said the efforts had suddenly halted for unclear reasons and the forces retreated.

With regards to the recent shelling of Islamic State, CNN Turk quoted a government official as saying Turkey was aiming to open a corridor for factions mostly focused on fighting Syrian President Bashar al-Assad, clearing the way for them to turn on Islamic State.

Ankara is a major backer of Syrian rebel factions fighting al-Assad, including Islamist groups, and appears keen to have these forces control territory on its border, rather than the Kurds.

Turkey is currently facing a Kurdish insurgency on its own territory and is concerned about growing nationalist sentiment among the minority group.

Kurds, a minority in Turkey and Syria, have long complained about systemic discrimination in both countries.

The Syrian Kurds have begun to carve out autonomous zones for themselves. Their latest military push appears aimed at linking up their eastern territory with a western enclave.

Backed by US-led alliance airstrikes, Kurdish-led forces have been a key group on the ground in driving Islamic State from territories in northern Syria.

Their advances have caused tensions between Ankara and Washington, which are likely to come up during Biden's talks with Turkish leaders, including President Recep Tayyip Erdogan.

Despite the Turkish shelling of their positions, the Kurds claimed they advanced against Islamic State and took more territory from the extremist group near Minbij, a key northern Syrian border area.

The US Department of Defence confirmed Monday that operations in the northern Syrian city of Minbij with the Kurdish-led forces are ongoing, amid a "broader effort to prepare defendable positions for long-term security."

Islamic State was driven from the city earlier this month, but left behind many booby traps which were being cleared.

Seizing Minbij is meant to help cut down on the flow of foreign fighters to Islamic State from across the still-porous Turkish border and weaken the extremist group's hold in northern Syria, according to Kurdish and US officials.

Biden is due in Ankara on Wednesday for a brief trip set to last hours. He will be the most senior official from Washington to come since the failed July 15 coup attempt in Turkey.

Purges since the failed Turkish coup have led to more than 1,600 officers, including many generals, being discharged. The military is also undergoing a shake-up, even as the country faces numerous security issues.

The US has said some of its key military interlocutors in Turkey were removed.

Biden and Erdogan are also to discuss Fethullah Gulen, a Turkish-born preacher living in the US. Turkey alleges Gulen, a former Erdogan ally, plotted the coup and wants him extradited, while Washington is asking for a formal request with evidence. Gulen denies the charges.

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