An Australian teacher has been shot dead in the Kenyan capital of Nairobi after dropping her son at a friend’s house.

Witnesses say Gabrielle Maina was walking down a street when she was attacked by armed men on a motorbike in the affluent suburb of Karen.

The motive for the attack is unknown, but it is believed it may have been a botched robbery.

“It’s a tragic event and our prayers and love and condolences go out to her family and loved ones,” Prime Minister Malcolm Turnbull told 3AW radio on Friday.

“She appears to have been killed in a fatal gunshot wound during a robbery.”

The shooting has shocked the expat community in Nairobi, especially students, teachers and parents from the Hillcrest International School, where Ms Maina was the head teacher.

In a statement provided to parents, the school expressed its condolences to Ms Maina’s family.

“It is with great sadness and shock that we are writing to let you know that Gabrielle Maina, Head Teacher of Hillcrest Prep has been tragically killed whilst out walking this morning,” the statement published by Fairfax Media read.

“She was returning home after dropping her son at a friend’s house.”

The school’s website says Ms Maina relocated to Kenya to establish her family in the country “so her children can grow up with their extended family”.

Ms Maina taught several subjects, including English, drama and Italian.

Ms Maina was originally from Armidale and was educated at the University of New England. She had many friends and colleagues in the NSW education sector.

An email to parents released by the school has expressed shock at Ms Maina’s death and offered condolences to her family.

It said the much loved teacher was attacked after she dropped her son at a friend’s house.

Police are investigating the killing.

The Department of Foreign Affairs and Trade (DFAT) is offering consular assistance to Ms Maina’s family.