Drachev was originally undercover inside the Middle Eastern insurgent cell for Russia, only to have his cover blown.

The battalion's efforts opened intelligence channels, forced insurgent cells to shift operations and locations, and expanded lines of communication in a sector previously dominated by the enemy.

The explosion, detonated by a technically advanced remote controlled device, was probably the work of an insurgent cell, he said.

American marines began an offensive sweep on Saturday through fertile farmland south of Falluja in an attempt to disrupt suspected insurgent cells in the area.

But as soon as one insurgent cell is broken up, another seems to move in.

American military officials have said Mosul is a caldron of diverse insurgent cells, with former Baathists and jihadists working to sow violence.

Many insurgent cells work together in western Iraq but remain independent of one another.

The new emphasis on attacking the insurgent cells and bomb-making factories outside the capital is expected to be a sustained one, involving tough fighting.

In that case, American attack helicopters and Iraqi forces struck an insurgent cell, killing several and capturing others.

Other insurgent cells were alerted by radio and "roof-top snipers killed perhaps a score" of Syrian soldiers.