SINGAPORE - A day after a group of gunmen massacred 132 children and nine staff in a school in Peshawar, Singapore's leaders expressed their shock and sadness at Pakistan's worst insurgent attack in years.

In a letter to Prime Minister of Pakistan Nawaz Sharif on Wednesday, Prime Minister Lee Hsien Loong said Singapore "strongly condemns this dastardly act of terror which has killed so many innocent young people".

Adding that he was "deeply saddened" to learn that many of the victims were students, Mr Lee said the incident "is a painful reminder of why we are fighting against the terrorist cause, and why we must remain vigilant and resolute in this long battle".

"I am confident that Pakistan will face this tragedy with fortitude, and in time prevail against the forces of darkness and evil," he added. He also offered his deepest condolences to the families of the victims and the Pakistani people.

Earlier on Wednesday, Mr Lee had noted on Facebook that the Peshawar attack came just a day after a gunman held 17 people hostage in a cafe in downtown Sydney, which led to three deaths including that of the gunman.

"Singaporeans know Sydney better than Peshawar, so the Sydney incident feels closer to home," he said.

"But when innocent children are brutally murdered like this our hearts go out to their families."

Foreign Affairs and Law Minister K Shanmugam also had strong words in reaction to the Peshawar attack.

"To target innocent children is abhorrent and cowardly. I can't understand what can make people kill innocent children," he said in a post on Facebook on Wednesday.

"Many of us will share the anguish of the families affected and my heart goes out to them."

Meanwhile, Deputy Prime Minister and Home Affairs Minister Teo Chee Hean expressed his sadness at the "tragic loss of innocent and young lives in Peshawar and Sydney."

In a Facebook post, he added: I hope that our prayers and thoughts can bring some comfort to their families and loved ones."