KIEV, Ukraine — A prominent couple who were fierce critics of President Vladimir V. Putin of Russia and who narrowly escaped an assassination attempt in June was attacked again on Monday. This time an assailant killed the wife and wounded the husband.

The couple, Amina Okuyeva and Adam Osmayev, had gained prominence in Ukraine as committed foes of both Mr. Putin and of the leader of the Russian region of Chechnya, Ramzan A. Kadyrov.

The attack was the latest in a string of assassinations and attempted assassinations in Ukraine, which the authorities in Kiev have mostly blamed on Russian special services. The murder of Ms. Okuyeva was the second attack in less than a week.

Still, her death was sure to be seen as especially tragic in Ukraine, because she had emerged as a heroine after the previous assassination attempt.