* Turkish security looking at links to Kurdish militants
* PKK in past has denied involvement in drugs trade
Turkish police seized five tonnes of marijuana with a street value of at least $2 million near the border with Iran on Tuesday and officials said they were investigating the involvement of Kurdish militants.
Turkish security sources say drug trafficking is a major source of income for the Kurdistan Workers' Party (PKK), which took up arms 28 years ago with the aim of carving out a Kurdish state in the southeastern border region with Iran and Iraq.
"Our security forces are investigating PKK links to the 144 sacks of marijuana seized today," an official at the governor's office in the city of Van, where the drugs were seized, said on condition of anonymity.
The PKK - designated a terrorist group by Turkey, the United States and European Union - has in the past denied any links to the drugs trade. In media interviews, its leaders have claimed it does not allow its members to use narcotics.
In 2009, U.S. authorities named several senior members of the group as suspected narcotics traffickers, freezing their assets and banning U.S. citizens from doing business with them.
Turkey is an important route for drug trafficking to Europe, since it is both a producer and an importer, mainly from Syria and Iran.
Turkey seized around 47 tonnes of marijuana in 2011, a 50 percent rise on the previous year, according to Turkish police figures. Van and the commercial capital Istanbul were among the cities with the highest seizures.