(Updates with comment by vigilante leader, background, in paragraphs 7, 16-17)
By Lizbeth Diaz
MEXICO CITY, Jan 27 (Reuters) - Mexico said on Monday it had captured a leader of the Knights Templar, a violent drug cartel that has created a major security problem for President Enrique Pena Nieto.
The attorney general's office said security forces arrested Dionisio Loya Plancarte, known as "El Tio" ('The Uncle'), a top member of the Knights Templar, which has clashed with vigilante groups in the western state of Michoacan this year.
He is the most senior member of the gang to be arrested.
The Knights emerged from a split in another cartel in Michoacan known as La Familia and have controlled large swaths of the restive mountainous state in recent years, extorting farmers and local businesses and diversifying away from drug trafficking to activities such as mining.
Plancarte is suspected of being the gang's go-between with corrupt security and justice officials, the attorney general's office said.
Mexico's government, which this month replaced top security officials in Michoacan, had offered a 30 million peso ($2.25 million) reward for information leading to Plancarte's arrest.
"It is a success, we are seeing the government doing its job and we are happy," Hipolito Mora, one of a clutch of vigilante leaders in Michoacan, told Milenio television.
The Knights' confrontations in January with heavily armed vigilantes in Michoacan have stirred concerns about Pena Nieto's strategy to combat widespread lawlessness in Mexico.
Since taking office in December 2012, Pena Nieto has sought to shift public attention to his efforts to reform the economy and away from grisly violence that has killed more than 80,000 people since his predecessor, Felipe Calderon, launched a military offensive against drug cartels seven years ago.
But security forces are still embroiled in face-offs with drug gangs in much of the country, and critics have accused Pena Nieto of lacking a clear strategy, arguing that there has been little change from Calderon's military approach.
Government officials say they are determined to capture Servando Gomez, leader of the Knights Templar, who has openly provoked the government by making regular public statements posted on the Internet, some of them via the media.
Though overall violence declined somewhat during Pena Nieto's first year, homicides rose in Michoacan, helping to spur the rise of heavily armed vigilante groups which this month occupied several of the Knights' strongholds in the state.
The government initially called on the vigilantes to disarm, but the so-called "self-defense" groups refused, and security forces are now tolerating their presence in much of Michoacan.
Pena Nieto said last week that some of the vigilantes had "genuinely organized to defend themselves".
The government's ambiguous attitude toward the local militias has fed concerns that it could be creating another potential adversary if the vigilantes become unmanageable - or if they too begin preying upon the local population.
The government has offered to incorporate the vigilantes into formal police ranks and give them training, in tandem with job-creating development programs.
"Most of us will join the police," Mora said on Monday, inking an agreement with the government that requires the vigilante group to submit a list of its members and to register their weapons.
Questions have been raised about who is arming and funding the vigilantes, with some locals and security analysts saying there is evidence rival cartels have infiltrated them. ($1 = 13.37 Mexican pesos) (Writing by Simon Gardner; Editing by Dave Graham, Kieran Murray and Mohammad Zargham)