Video: Pakistan security forces try to free passengers from train siege

Islamabad: Pakistan forces launched a "full-scale" operation on Wednesday to rescue train passengers taken hostage by militants in the mountainous southwest, with security sources saying 190 had been freed in the past 24 hours.

More than 450 passengers were on board when militants captured the train at the entrance of a tunnel in a remote frontier district, with an unknown number of hostages still being held. 

"Information suggests that some militants have fled, taking an unknown number of hostages into the local mountainous areas," a security official in the area told AFP.

Militants bombed a section of the railway track and stormed the train on Tuesday afternoon in southwest Balochistan province, which borders Iran and Afghanistan, where attacks by separatists have risen sharply in the past year.