Speaking at a news conference in Brussels yesterday with European Commission President Jean-Claude Juncker, Stoltenberg said NATO was pushing ahead with the deployment since it was approved last month.
"There are now five ships in the area, there will be more ships in the coming days, and we also have helicopters on most of the ships, so we are increasing the presence of NATO vessels with modern equipment," Stoltenberg said.
The vessels were concentrating on the area around the island of Lesbos and aimed to "cut the lines of the illegal networks and illegal trafficking of people across the Aegean Sea."
Britain announced on Monday, ahead of an EU summit with Turkey on the migration crisis, that it was sending an amphibious landing ship and several other vessels to join ships from Canada, Germany, Greece and Turkey.
NATO launched the deployment, the first civilian operation of its kind for the military alliance, after a request by Greece, Turkey and Germany to help tackle Europe's biggest migration crisis since World War II.