Riga's plans to impose Latvian as the main teaching language in minority schools has created tension among some of its ethnic Russian population, resurrecting a long-running dispute with Latvia's former Soviet masters.

In the Baltic nation, where around a quarter of the population is ethnic Russians, only about 40 percent of classes in minority schools are taught in Latvian.

In March, however, parliament voted through legislation which will raise that to 80 percent, meaning from September 2019, all core subjects will be taught in Latvian.

Latvia says the aim is to improve end-of-high-school exam results, which are crucial for obtaining state-sponsored college tuition. Such exams are only in Latvian, a Baltic language with little similarity to Russian, which is Slavic. But the move has been denounced as "discriminatory" by some of Latvia's Russian minority who have staged months of protests, with Russia's Organization for Security and Co-operation in Europe (OSCE) envoy and even President Vladimir Putin weighing in, citing "human rights" violations. "I hope they are ashamed because they pay special attention to human rights violations outside the European Union, but they themselves violate human rights within the EU," Putin remarked earlier this month.

Within Latvia, ethnic Russians constitute by far the largest minority, accounting for 24 percent of the population of 1.9 million people. Latvians make up 62 percent, while the rest mainly include individuals of Belarussian, Polish or Ukrainian descent.

During the Soviet occupation which began during World War II, tens of thousands of Latvians were deported and equal numbers of ethnic Russians were shipped into the Baltic state by Moscow, altering the ethno-linguistic profile of the country.

At that time, there was a Russification policy in place which saw the establishment of a separate Russian-language school system, with 94 Russian-only and 57 bilingual schools still in existence.