This article was originally published March 28, 2014.

Around the world, many territories are claimed by more than one country. Disputes over these territories can lead to growing tensions between countries, and sometimes even war. There are now more than 150 territorial disputes underway. They mostly involve territories in Africa, Asia and the Pacific region, but also in Europe and the Americas. Some disputes are tense but relatively quiet, while others are at their boiling point.

Some of the most worrying territorial disputes are listed below.

Crimea

In 1954, Crimea became a part of Ukraine, even though the majority of the population was Russian, not Ukrainian. At the time, both Russia and Ukraine were part of the Soviet Union. In 2014, Russian military forces took over Crimea with the help of pro-Russian Crimeans. A referendum, or countrywide vote, was then held to determine if Crimea should become part of Russia. The vote came out in favor of Crimea joining Russia.

Most world leaders said the vote had not been open and fair. They claimed Russia had illegally seized Crimea. The Ukrainian government said Crimea should still rightfully be a part of Ukraine. Western Europe and the United States quickly imposed economic sanctions on Russia. An economic sanction is when countries stop trading with another country or impose other punishments on that country's economy.

Jeffrey Mankoff is an expert on Russia based in Washington, D.C. He fears that Russia's annexation of Crimea will set a bad example. For example, he said, China may decide it can get away with doing the same thing.

East China Sea and Tibet

A chain of islands in the East China Sea is claimed by both Japan and China. They are known as the Senkaku Islands in Japan and the Diaoyu Islands in China. Tensions have risen between the two countries as a result.

China is also involved in many other territorial disputes, including the long struggle over Tibet. The struggle over Tibet "is an example of a dispute where there is one state and an area inside it wants to be separate," said political science professor Ron Hassner. Because of its size, Tibet would top his list of current disputes, Hassner said. Both its territory and its population are quite large.

Jammu and Kashmir

Jammu and Kashmir was once part of British-controlled India. After Britain gave up control of India in the 1940s, Jammu and Kashmir was divided up between India, China, and the then-new country of Pakistan. There is now a 724-kilometer- (450-mile-) long border separating the Indian part of Jammu and Kashmir from the Pakistani part. Both nations have many troops stationed along this border, which is known as the Line of Control.

India and Pakistan both lay claim to all of Jammu and Kashmir. Because both countries have nuclear weapons, this dispute worries many around the world. If it leads to war, the consequences could be terrible.

Golan Heights, Gaza Strip and the West Bank

The Gaza Strip and the West Bank are claimed by both Israelis and Palestinians. Both territories are just tiny pieces of land, but the disputes over them have been long and bitter. Over the years, many people have been killed during protests and military actions.

The Golan Heights dispute is between Israel and Syria. It has been underway for decades, since Israel annexed the territory following the 1973 Yom Kippur War. Because Syria is now caught up in a bloody civil war, the Golan Heights dispute is no longer a major focus.

Western Sahara

Until 1976, the northwest African territory known as Western Sahara was a Spanish colony. After the Spanish left, Morocco succeeded in annexing the 259,000-square-kilometer (100,000-square-mile) territory. However, Morocco's annexation has not been recognized internationally, and its control has been disputed ever since. Morocco has built a 3,219-kilometer- (2,000-mile-) long series of walls to push the native population, the Sahrawis, out of the area. A number of people have been killed in clashes between protesters and Moroccan security forces.

Transdniestria

Besides Crimea, Russia is involved in several other territorial disputes. The region many are worried about is Transdniestria, a tiny strip of land that lies between Moldova and Ukraine. Transdniestria is currently an unrecognized breakaway state.

Transdniestria proclaimed independence from Moldova and allegiance to Moscow in the early 1990s. Since then, Russian troops have been stationed in the country. After Russia annexed Crimea, local leaders said they strongly hoped to be annexed next. So far, that has not happened.