The U.S. Justice Department says the number of people jailed in the United States last year rose nearly three percent, the biggest increase in six years.

A report released Wednesday said local, state and federal prisons together held more than 2.2 million people as of June, 2006.

The United States already had the world's largest prison population, followed by China and Russia.

The report shows that African American and Hispanic males make up a disproportionate number of those imprisoned.

Criminal justice experts attribute the rise in the U.S. prison population to tough sentencing laws and record numbers of drug offenders.

Some information for this report was provided by AFP, AP and Reuters.