Ghurkhas previously deployed in Sierra Leone
Three hundred Gurkha troops have been deployed in Sierra Leone to help counter insecurity in neighbouring Liberia, according to the British Defence Ministry.
The recent arrival of the Nepali soldiers is the first time the British army has substantially reinforced its positions in Sierra Leone since it began reducing its presence two years ago.
"Over the last few weeks there have been elements of rebel activity over the Liberian border which may destabilise the situation, but there was no specific or dramatic development last week itself to trigger the deployment," an army spokesman said.
Rebels in Liberia have recently been making advances against government troops.
The Sierra Leone war was declared over in January last year and peaceful elections were held a few months later.
There have been reports of thousands of refugees crossing the Liberian border into Sierra Leone to escape the fighting.
A spokesman for the United Nations force in Sierra Leone said UN soldiers were on the Sierra Leone side of the border backing up "a robust government army presence".
UN commanders recently crossed into Liberia to warn the Liberian rebels not to enter Sierra Leone.
More than 120 British military advisers continue to train the newly-trained Sierra Leone army.
The British intervened at the height of the brutal 10 year Sierra Leone civil war to save the democratically elected government from being overthrown by rebels.
They also came to back up a United Nations peacekeeping force that came under severe rebel attack.
The country still boasts the largest UN peacekeeping force in the world.
A shooting incident last month in the capital, Freetown, led to many arrests and raised fears of a coup attempt.