Kazakhstan's domestic security agency says five gunmen suspected of involvement in recent armed attacks in the city of Aktobe have been killed in a security sweep.

The National Security Committee said its agents early Friday tracked down a group of four suspected militants hiding in an apartment building in Aktobe, a city in Kazakhstan's northwest, about 70 kilometers (some 45 miles) south of the Russian border. It said the suspects refused to surrender and were all killed in a gunbattle.

Another gunman fired at police at a different location and was killed by retaliatory fire. Two police officers were wounded.

A series of attacks on a military base and gun shops in Aktobe Sunday killed 20, the worst violence the ex-Soviet Central Asian nation have seen in years.