ISLAMABAD -- Pakistani security forces have killed 27 terrorists and rescued 155 passengers during an ongoing operation to rescue hostages following a train attack in the country's southwest Balochistan province, security sources said on Wednesday morning.

The incident happened in Kacchi district of the province on Tuesday when the train Jaffar Express, carrying about 450 passengers in nine bogies, was traveling from provincial capital city of Quetta to the country's northwest city of Peshawar on Tuesday when an unknown number of terrorists stormed the train and took passengers hostage, security forces told Xinhua.

The security sources said the operation to eliminate the terrorists is underway, who split into small groups with hostages and used them as human shields to hinder the operation.

"The terrorists wearing explosive vests, have positioned suicide bombers near innocent hostages, making the rescue operation increasingly challenging," the sources added.

Security sources further revealed that the terrorists are in contact with their facilitators in Afghanistan, coordinating their actions as security forces intensify efforts to neutralize them and ensure the safe recovery of the remaining hostages.

The noose around the terrorists has been tightened, and the operation will continue until the last terrorist is eliminated, the sources added.

Earlier, railway officials confirmed that 57 rescued passengers were transported to Quetta in the early hours of Wednesday, while 23 others remained in Mach, a town of Balochistan.

In response to the crisis, the Balochistan government has declared an emergency and mobilized all relevant institutions to manage the situation, provincial spokesperson Shahid Rind said.

A relief train, along with security reinforcements, was dispatched to the site to assist in the rescue operation, he added.

Additionally, emergency measures have been enforced at Sibi and Civil Hospital Quetta to provide immediate medical aid to those affected.

"The attack occurred in a mountainous region where communication is severely restricted due to the lack of mobile service. In the last contact with the train, the driver reported that an explosion hit the railway track, forcing the train to stop. Immediately after, the militants opened heavy fire, injuring the driver and several passengers," Senior Pakistan Railways official Muhammad Kashif told Xinhua.

Pakistani Prime Minister Shehbaz Sharif strongly condemned the attack on the train, praising the security forces for their bravery and professional expertise in confronting the terrorists.

"Despite the difficult terrain, the morale of the security forces involved in the operation remains high. We will continue this war against terrorism until this menace is completely eradicated from the country," the prime minister said.

Sharif added that every conspiracy aimed at spreading unrest and chaos in Pakistan would be foiled, and "we will never allow the evil intentions of anti-state elements to succeed."

The proscribed terrorist outfit Balochistan Liberation Army (BLA) claimed responsibility for the attack in a statement on a social media platform.