Gunmen seized part of a northern Iraqi town and nearby villages Thursday, while bombs killed at least two people at a historic Baghdad market and set it ablaze, officials said.

The takeover in and around the Salaheddin provincial town of Sulaiman Bek comes as gunmen control all of one major city and part of another in the western province of Anbar in a stand-off that has lasted for weeks and displaced hundreds of thousands of people.

It illustrates the scope of the security problems the country faces, the reach of militant groups and the inability of the armed forces to bring them under control. […]