1.   But there have also been several unexplained bomb explosions around the country in the last two years.

2.   By the time an unexplained bomb goes off one day in Knightsbridge, the cliches are almost as noisy as the ensuing sirens.

3.   A series of unexplained bombs have also hit the country.

4.   Indonesia has been hit by a new wave of unexplained bomb attacks recently.

5.   The Netherlands has seen a series of unexplained bomb attacks in recent months.