Some 1,500 Turkish-backed Syrian rebels have also gathered in the Turkish city of Gaziantep, poised for an offensive to drive IS out of Jarablus.
Turkey has also shelled Syrian Kurdish forces nearby, apparently to deter them from taking Jarablus themselves.
Gaziantep was hit by a suicide bombing on Saturday which killed 54 people.
The BBC's Mark Lowen in Gaziantep says the attack on a wedding in the city, blamed on IS, may have been  spurred by reports of the imminent Syrian rebel offensive.
More victims of the blast are being identified and our correspondent says the wave of bombings in Turkey could intensify as the country becomes ever more embroiled in the Syrian war.
Turkish Foreign Minister Mevlut Cavusoglu has said that IS should be "completely cleansed" from areas in northern Syria near its border.
Turkish forces have been exchanging shellfire with IS positions in the Jarablus area since Monday.
However, Turkey is also wary of moves that might bolster Syrian Kurdish forces, known as the YPG, which it views as an extension of the Kurdistan Workers Party (PKK), a Turkish-Kurdish rebel group fighting for autonomy since the 1980s.
On Monday, Turkey shelled YPG positions near Manbij, a town they took from IS this month.
The 1,500 fighters poised to enter Syria from Gaziantep are believed to be Turkish-backed Syrian rebels. A senior rebel official quoted by Reuters said they were fighting under the banner of the Free Syrian Army.
The identity and motive of the suicide bomber who attacked the wedding party have yet to be revealed.
Soon after the attack, President Recep Tayyip Erdogan said IS was the likely perpetrator but Prime Minister Binali Yildirim said on Monday that investigators actually did "not have a clue".
He downplayed earlier reports that the attacker was between 12 and 14 years old, saying this could not be confirmed.
The pro-Kurdish Peoples' Democratic Party (HDP) said the wedding was for one of its members, and IS have targeted Turkish Kurds in the past.
Many of the victims were children - the two youngest were four years old.
Sixty-six people are still in hospital, 14 of them in a serious condition, Turkey's Dogan news agency reported.
A disproportionately large number of women and children were killed in the attack because it targeted henna night, a part of the celebration attended mainly by women and children, says BBC Monitoring's Turkey analyst Pinar Sevinclidir.
Syrian government forces are not directly involved in the battle for the border at Jarablus, having gradually lost ground in the north over more than five years of civil war.
Turkey's long-time position has been that President Bashar al-Assad must be ousted as a condition for peace in Syria.
However, Prime Minister Yildirim acknowledged this week that he was one of the "actors" and  suggested he could play a role in an interim leadership.

Five-time world champion O'Sullivan came from 3-0 down to level the match before fellow Englishman Holt took the deciding frame with a break of 76.
Compatriot Peter Ebdon, 30th in the rankings, shocked world number three Neil Robertson 4-3 at Venue Cymru.
Ebdon now faces China's Ding Junhui, who beat 4-3 Englishman Ben Woollaston.
World number 31 Holt made a brilliant 119 and 88 to establish an early advantage against O'Sullivan, but last year's runner-up compiled an 86 as he drew level.
O'Sullivan missed a red to the centre in the decider as Holt set up a second-round meeting with Liang Wenbo or Graeme Dott.
Joe Perry beat Barry Hawkins 4-0, and fellow Englishman Martin Gould saw off China's Tian Pengfei by the same margin.
In round two, Perry will play the winner of Wednesday's match between Welshman Jamie Jones and England's Kyren Wilson.
Gould faces Michael White or Shaun Murphy, the 2005 world champion, in the next round.
Ryan Day progressed with a 4-1 win over Matthew Selt, while John Higgins beat fellow Scot Stephen Maguire 4-0.
The winner of the Grand Prix will earn £100,000 in prize money.
Turkey has bombarded so-called Islamic State (IS) targets across the border in northern Syria ahead of an expected ground attack on an IS-held town.
[NEXT_CONCEPT]
Michael Holt survived a Ronnie O'Sullivan comeback to win 4-3 in the first round of the World Grand Prix in Llandudno.