The former Vice President particularly referred to the killing of a British aid worker, Faye Mooney in Kaduna.
She was shot dead after gunmen stormed a holiday resort last Friday, killing two people and kidnapping three others.
The British High Commission confirmed her death, and non-governmental aid agency Mercy Corps named her as Faye Mooney, one of its employees in Nigeria.
Abubakar told the UK not to use the killing of the worker to judge Nigeria’s character.
He condemned the atrocious actions of the attackers and the bad image it has portrayed to the international community.
“I want the government and people of the United Kingdom to know that these atrocious actions do not reflect Nigeria’s national character.
“I condemn the killing of British aid worker, Faye Mooney, and her Nigerian partner, Mathew Oguche two days ago in Kaduna State. Several other Nigerians were kidnapped during the episode”.
The continuous killings would lead to the loss of investments and partners who are interested in the growth and development of the economy.
“These killings must end or Nigeria will lose desperately needed friends, partners and investors.
“Not only do I condemn this recent killing, but I make an urgent call for the federal and state authorities to track down the culprits and make them pay for their crimes.
“The time for empty rhetoric is long gone. Now is the time for urgent national action to stem insecurity. Nigeria must once again become synonymous with peace, progress and prosperity. This can only happen when crime and punishment are a natural cause and effect.
“As long as there is impunity, our nation will lack unity and security. Impunity must end and must end in earnest. These crimes continue to reoccur because previous killings have not been met with justice”
He called on Federal Government to track down the culprits and also keep Nigeria safe for its people and for foreigners coming in and out of the country.
“We need to keep Nigeria safe for Nigerians and foreigners. The death of any Nigerian or foreigner from terror, crime or insecurity grieves my heart. Nobody’s life is worth taking to advance a religious, political or criminal cause”.