Any attempt to rescue a Danish family captured by pirates in the Indian Ocean will result their deaths -- just like the four American sailors slain by their captors last week, a Somali pirate warned Tuesday.

Maritime experts said the Danes -- a couple with three teenage children aged 12 to 16 -- placed themselves in grave danger by sailing into pirate-infested waters off Somalia's lawless coast despite warnings from naval forces struggling to police the area.

The family was captured Thursday by pirates along with two Danish adult crew members after sending a distress signal from their sailboat, the Danish government said, adding it was doing "everything in our power" to help them.

Abdullahi Mohamed, a pirate who told The Associated Press he has ties to the gang holding the Danish family, said they will be killed if any rescue operation was carried out. He specifically referred to the killings last week of four American hostages captured by pirates on their yacht.

Mohamed has provided reliable information to AP in the past on piracy.

The American deaths were a game-changer in the world of piracy. Somali pirates have captured hundreds of ships and thousands of crew members over the years -- right now they have 660 hostages and some 30 vessels. But virtually all the hostages would be released unharmed after pirates negotiated multimillion-dollar ransoms for them and their ships.

Companies paid the ransoms with insurance money and rarely attempted rescue missions to ensure the safety of their employees. If a ship's owner was unable to pay the amount demanded, pirates would keep the boat and use it to stalk other vessels on the high seas.

Mohamed said pirates were discussing how much ransom to demand for the Danish hostages, and added that investors backing the pirate gang were angling for a large sum.

A British sailing couple was released in November after more than a year in captivity. Reports varied how much was paid for their release, but it was believed to be around $1 million. Pirates are now commanding roughly $5 million per hijacked ship.

The Danish family knew about the hijacking of the American yacht, according to a travel blog in which they chronicled their round-the-world journey that began in 2009. It was not clear, however, if they knew about the Americans' deaths.

"Of course, we talked quite a lot about it (the American hijacking) but this is far over thousands of kilometers (miles) away and the Arabian Sea that we sail in is the size of Europe," the family said a Feb. 20 posting on ING jordenrundt.info. ING is the name of their boat.

Two days later, the Americans were killed.

The Danish family's last posting on Feb. 23 -- a day before their own hijacking -- only said their journey was uneventful and "we have NOT been boarded by pirates."

The blog identified the family as Jan Quist Johansen, his wife Birgit Marie Johansen, their sons Rune and Hjalte and their daughter Naja. They are from Kalundborg, 75 miles (120 kilometers) west of Copenhagen.

The chairman of the Kalundborg yacht club, Ole Meridin Petersen, confirmed their names to The Associated Press. He called them "experienced sailors" and said they were planning to enter the Mediterranean from the Red Sea via the Suez Canal and get home by August.

That route would take the family through the Gulf of Aden, one of the most dangerous waterways in the world in terms of piracy.

The Johansens had been sending daily position and status updates by e-mail since Feb. 17 to the British Royal Navy's UK Maritime Trade Operations, which acts as a liaison for ships traveling through waters threatened by pirates, said Wing Cmdr. Paddy O'Kennedy, a spokesman for the European Union's anti-piracy force.

He said the EU Naval Force had written an open letter to European governments, yachting organizations and magazines warning of the dangers of sailing through the area threatened by pirates.

"We did everything we possibly could to advise the yachting fraternity of the danger," O'Kennedy said. "They (the family) were aware of the risks they were about to take."

The EU and other warships do not provide escorts for individual ships, although they do patrol a maritime corridor that shipping is urged to stick to. Reporting a daily position, like the Johansens did, might give a warship a slightly quicker reaction time but even that doesn't mean help could reach the ship under attack in time, he said.

"Even traveling in groups is not a protection for yachts. It's just a bigger target for the pirates," he said. "When you're on a yacht, it can take seconds from when (the pirates) are seen to when they're onboard."

Per Gullestrup, head of Danish shipowner Clipper, said it was "totally insane" for a yacht to sail on its own into waters where much bigger commercial ships often travel in convoys and hire armed guards for protection against pirates.

"They sailed right into the pirates' arms," said Gullestrup, whose company owns a cargo ship that was held by Somali pirates for more than two months in 2009.

Since 2008, there have been at least nine hijackings of private yachts in the region, said Hans Tino Hansen, who runs a company specializing in maritime security.

"Sailing boats and small private yachts are very difficult or impossible to secure against pirate attacks due to their low speed and low freeboard," Hansen said.

In the blog, family members wrote that they saw overflights by counter-piracy patrol planes. "It is reassuring that they look after us," a Feb. 20 post said. A day earlier, the family blogged they had drawn up "a piracy plan for who does what if we are attacked."

Somali pirates have extended their range east and south after increased naval patrols in the Gulf of Aden.

The pirates have rarely captured families and children, but a 3-year-old boy was aboard a French yacht seized in 2009. French navy commandos attempted a rescue, but two pirates and the boy's father were killed in the operation. Four French citizens were freed, including the child.

Denmark's Foreign Ministry on Tuesday advised citizens against traveling in sailboats in the Gulf of Aden, the Arabian Sea and the northwestern Indian Ocean.