Ken McCallum said the number of state-threat investigations undertaken by MI5 has risen by 48 percent in the past year.
Ukrainian military calls situation ‘unstable’ with fighting at ‘every entrance’ of front-line city.
Defence minister says ‘highly likely’ North Korean soldiers were killed in recent attack by Ukrainian forces.
Stephen Hubbard, 72, was detained in eastern Ukraine in April 2022 and accused of fighting for Ukraine.