Cpl Binnie was part of a Battlegroup mentoring the Afghan army
Two UK soldiers have died in an attack in southern Afghanistan's Helmand province, bringing the total killed on Thursday to four.
A soldier from 1st Battalion The Royal Gurkha Rifles and one from 173 Provost Company, 3rd Regiment, Royal Military Police died after a suicide attack.
Another soldier, from 2nd Battalion The Rifles, died in an explosion.
A Black Watch soldier who was shot near Musa Qala in Helmand has been named as Cpl Sean Binnie, 22.
The families of all the soldiers have been informed.
Since 2001, 157 UK troops have been killed on operations in Afghanistan.
Almost 500 troops from the Black Watch left their home base at Fort George just outside Inverness in March to begin a six-month deployment in Afghanistan.
Cpl Binnie, from the 3rd Battalion The Royal Regiment of Scotland, is the first Black Watch soldier to be killed on this latest tour.
Our married life has been a short six months and I'm speaking for both of us in saying it was the best six months ever
Most of the Black Watch are deployed in Kandahar but Cpl Binnie died from a bullet wound received on a reassurance patrol with the Afghan National Army in Helmand.
Family and colleagues of Cpl Binnie have been paying tribute to a brave and valued soldier.
His wife, Amanda, said: "My husband, my hero - you have been so strong and brave.
"Our married life has been a short six months and I'm speaking for both of us in saying it was the best six months ever."
Lt Col Stephen Cartwright, commanding officer of his battalion, said his death had come as a "great blow".
He said Cpl Binnie had given his life in service of others in the career that he loved and had died in the defence of his friends and his comrades in the Afghan National Army.
"Sean was full of life, always cheerful and a loyal junior non-commissioned officer: he will be missed by us all but will not be forgotten," he added.
The soldiers killed by the suicide attack died during a patrol in Gereshk, Helmand Province.
Speaking of their deaths, Lt Col Nick Richardson said: "With heavy heart we report another extremely sad situation, where lives of our courageous soldiers have been sacrificed for the greater good of the Afghan people.
"Our deepest and heartfelt sympathies go to their families and loved ones and we offer our thoughts and prayers to them all at this most painful and distressing time."
Brigadier-General Richard Blanchette, spokesman for the Nato-led International Security Assistance Force in Afghanistan, said the soldier from 2nd Battalion The Rifles had made the "ultimate sacrifice to bring hope and peace to the people of Afghanistan".
The soldier was killed in Sangin, in the north of the province.
This is the first time since June 2008 that four soldiers have been killed on a single day. Four Royal Marines died in two separate incidents in Helmand in December 2008.