At least 21 people were killed and 46 others injured on Saturday in a powerful bomb explosion at a crowded railway station in Pakistan’s restive Balochistan province, officials said. The blast ripped through the provincial capital, Quetta’s railway station, as passengers gathered on the platform before the scheduled departure of the Jaffar Express to Peshawar. The banned separatist militant group in the area, the Baloch Liberation Army, claimed responsibility for the attack in a statement.

Rescue and law enforcement teams immediately rushed to the site to secure the area, with the injured being taken to Civil Hospital in Quetta. The hospital declared an emergency, with extra staff to manage the influx of patients.

Officials believe a suicide attack may have caused the blast, though this has not yet been confirmed. The number of casualties is expected to rise, according to police spokesperson SSP Operations Muhammad Baloch. According to reports, most of the injuries were caused by the first blast that hit bogie No. 3. The second explosion took place just seconds later, hitting a train carriage but causing only a few casualties because most passengers had already left the coach before the attack.

The BLA is fighting for independence for Balochistan, Pakistan’s largest but least populated province, borders Afghanistan to the north and Iran to the west. The group is one of several ethnic insurgent groups that accuse the central government of neglecting the province and exploiting its natural resources.

On Tuesday, the government launched a major operation against insurgents in Balochistan. The military action is aimed at tackling the growing number of attacks by separatists on government buildings and highways.

Balochistan Chief Minister Sarfraz Bugti condemned the attack and ordered an immediate investigation. He said those responsible for targeting innocent civilians will be brought to justice.

The attack comes just a week after a powerful bomb attached to a motorcycle exploded near a vehicle carrying police officers assigned to protect polio workers in a town in Balochistan’s Mastung district, killing nine people, including five children. The provincial government has imposed an emergency in the hospitals where all the wounded are treated.

In a separate development, the government has also banned importing and selling ammunition for small arms from foreign suppliers and imposed stiff penalties on those who break the ban. It has also increased security in the rest of the province to prevent such incidents from happening.

The federal government and local lawmakers have expressed solidarity with the victims of the attack, and Prime Minister Shehbaz Sharif has promised to take steps to bring those responsible to justice. He has urged security forces to continue their efforts against terrorism. He has also pledged to build the railway link to Gwadar and make it a hub for trade with China as part of his country’s massive ‘Belt and Road’ infrastructure project. The deteriorating security situation in Balochistan is of particular concern to Beijing, which has poured billions into the region in recent years.