Mumbai and other major Indian cities were put on a state of high alert Wednesday after three explosions rocked the commercial hub, killing 18 people and wounding dozens. Indian Prime Minister Manmohan Singh requested the residents of Mumbai to stay calm and united. No group has yet claimed responsibility for the explosions, which occurred during evening rush hour in three districts. According to Indian Home Minister P Chidambaram, he believes the explosions were “a coordinated attack by terrorists”, since they took place within minutes of each other. The attacks were the deadliest in the city since Nov 2008 when 10 terrorists launched a coordinated operation killing 166 people.