By Jeremy McDermott BBC correspondent in Colombia

Raids have been targeting property of alleged drug barons

Over 100 properties, including luxury villas, have been seized.

If the properties can be proven to have been bought by earnings from drugs, they can be sold and the money sent to Colombia's depleted treasury.

The estimated value of the assets is $150m and income from their sale would help fund the continuing war on drugs.

The Colombian government, strapped for cash as it fights a civil conflict entering its fifth decade, has increasingly turned to seizing the assets of drugs traffickers, then selling them.

Don Diego, acknowledged as the head of the last great cartel, that of Norte del Valle, has long been a target not just of the Colombian authorities but of the United States.

Washington has offered a record $5m for any information leading to his capture.

With the fall of the cartels of Medellin and Cali, their place was taken by Norte del Valle.

When this cartel falls, which seems imminent, there will not, however, be any interruption in the flow of drugs from Colombia, estimated at 800 tonnes of cocaine and 10 tonnes of heroin every year.

The place of the big cartels has been taken by even more dangerous and powerful forces - the country's Marxist guerrillas and right-wing paramilitaries.