MOSCOW, July 6 (RIA Novosti) - Two Chechen police officers were wounded after setting off a mine during the pursuit of up to 20 militants believed to be behind an attack that killed nine of their colleagues in Russia's Ingushetia.

"Two Chechen police officers were wounded in a bomb explosion during a special operation in Ingushetia's Sunzha district while pursuing a militant group, which earlier ambushed a convoy of Chechen police," a source in the Ingush police said on Monday.

The motorcade of Chechen police was ambushed on Saturday in Ingushetia's Sunzha district, bordering on the Chechen Republic, during a special operation of the Chechen and Ingush interior ministries against suspected militants.

The continuing operation was launched after Chechen President Ramzan Kadyrov had vowed tough measures against the assailants, saying they would be held responsible for the attack.

Russia's North Caucasus has seen an upsurge in violence of late, with the killing of Daghestan's Interior Minister Adilgerei Magomedtagirov and an assassination attempt on the Ingush President Yunus-bek Yevkurov last month.

The increase in violence has coincided with Moscow's decision to formally end its decade-long counterterrorism operation in Chechnya, which witnessed two brutal separatist wars in the 1990s and early 2000s.