According to Karl Popper's falsification criterion only a falsifiable theory is said to be a scientific theory. If this is true, is Economics falsifiable and hence considered scientific?
It is not possible to falsify economics or science. You are conflating theories, methods, and disciplines. Good theories are falsifiable, disciplines are not. Like most disciplines, some aspects are falsifiable and others are not, and that a discipline has some aspects that are not falsifiable doesn't eliminate it as a science. A perfect example is astronomy which studies many phenomena that cannot be falsified directly. Karl Popper and his critical rationalism was a great counterweight to the logical positivists he criticized, but falsification is only one aspect of what generally constitutes scientific methods. To boot, economics does have theories that can be tested such as those of behavioral economics, among others. What constitutes a science is subject to controversy and interpretation, such as the dispute between realists and intstrumentalists.
Besides, falsification can be practiced in economics through trial and error in fiscal policy. A classic example of an often touted, but thoroughly discredited economic theory is that of trickle-down economics. Supply-side economic theory has been tested as fiscal policy repeatedly over the last hundred years, and the effects consistently fail to create economic growth. Money simply doesn't trickle down, the most recent evidence is recent Kansas fiscal policy.
By most reasonable definitions of a science, economics passes muster.