A suicide bombing killed a judge and 15 others inside a courtroom in southwestern Pakistan Saturday, the deadliest in a string of attacks that have rattled the country in recent weeks. But authorities said they were in the dark about the latest blast that also wounded 24 in Quetta District Courts. It forced police - already on alert - to further tighten security nationwide. Authorities, including Jam Mohammed Yousaf, the top elected official in Baluchistan province of which Quetta is the capital, hinted at Afghan involvement, but gave no evidence to back up the claim. Relations between the neighboring countries have soured over Afghan allegations that Pakistan is supporting Taliban militants who have escalated their campaign of violence in the neighboring country over the past year. Pakistan denies helping the militants but acknowledges that some operate from its soil.