DUSHANBE (Reuters) - Tajikistans forces have shot dead a suspected rebel accused by the authorities of spearheading an armed insurgency on the countrys border with Afghanistan, a senior security source said on Wednesday. Pakistans President Asif Ali Zardari and Afghanistans Hamid Karzai were both in Tajikistan for talks on security in Central Asia, a key transit route for supplies for US troops fighting the Taliban in Afghanistan. Russian President Dmitry Medvedev was due to arrive later as part of a regional summit. The security source said that the rebel Nemat Azizov was killed as a result of a special operation in Tajikistan. Two gang members were killed ... overnight. One of them was Nemat Azizov, the source told Reuters. Earlier this month, unidentified gunmen attacked a police post near Tajikistans border with Afghanistan and engaged in a lengthy gun battle with Tajik forces. Five militants were killed, according to Tajikistans authorities.