But mujahedeen sources in Quetta, southeast Pakistan, said Friday's attack was first planned five months ago and was apparently aimed to avenge a similar attack by government troops 11 years ago.
Najib has accused Pakistan of deploying about 15,000 soldiers across the border near Quetta to help in an attack on Kandahar, which is about 200 miles from Kabul, the capital.
Two people were killed and about seven injured in one such flare-up in Quetta in January.
US should not intervene alone, Page 2 A Briton from the deputy high commission in Karachi is one of three European diplomats who have disappeared after a joint official visit to the city of Quetta, Baluchistan, the Foreign Office said.