The death toll from a bombing at a Sufi shrine in southern Pakistan on Saturday rose to 52, with 105 injured, home minister for the southwestern Balochistan province said.
"At least 52 people have been killed and some 105 others wounded," said Sarfraz Bugti.
The Islamic State group has claimed a suicide bomber targeted the shrine, but the minister said it was not immediately clear if this was a suicide attack.
The blast hit a crowd of worshippers participating in a ceremony at the shrine of the Sufi saint Shah Noorani in Khuzdar district, some 750 kilometres (460 miles) south of provincial capital Quetta.
Local officials said worshippers were taking part in a devotional dance session, which is held daily before dusk, when the blast occurred.
Rescuers were scrambling to reach the shrine, which is located in a remote, mountainous region with limited medical facilities.
Authorities have dispatched ambulances and medical workers from Karachi, a three-hour drive from the blast site.
Islamic State claims responsibility
Pakistan Army spokesman Lieutenant General Asim Bajwa said troops and medical teams had been dispatched but that "difficult terrain and long distance" were hampering their progress.
Bajwa said that 20 ambulances and 50 soldiers were about to reach the site, while a further 45 ambulances 100 troops were also on their way, along with medical teams.
A military helicopter would attempt evacuations at night, he added, but medical teams could not access the area by plane as there were no airstrips close by.
President Mamnoon Hussain and Prime Minister Nawaz Sharif strongly condemned the bombing in separate statements.
"The government is determined to eliminate terrorism and extremists from the country," Hussain said in a statement expressing sympathy for the victims and their families.
A statement from Sharif's office said the prime minister called for the "best medical treatment" to be given to the wounded.
Up to 600 people were at the shrine at the time of the attack, according to local official Tariq Mengal, who told Geo TV that many devotees travelled to the site from Karachi during weekends.
The Islamic State group claimed responsibility for the attack via Amaq, its affiliated news agency.
"35 dead and 95 wounded Shiite visitors in a martyrdom operation attack by the Islamic State fighter that targeted a shrine in a city in Balochistan," the agency said.
The bombing follows the killing of Amjad Sabri, a renowned Sufi singer, by two gunmen in Karachi in June.
Some observers have said that Sabri may have been assassinated because he was a high-profile Sufi.
Sufism, a mystic Islamic order that believes in living saints, worships through music and is viewed as heretical by some hardline groups including the Taliban.
Balochistan, which borders Iran and Afghanistan, has oil and gas resources but is afflicted by Islamist militancy, sectarian violence between Sunni and Shiite Muslims and a separatist insurgency.
Local militants claimed to have worked with the Islamic State group to attack a police academy in Balochistan last month, killing 61 people in the deadliest assault on a security installation in Pakistan's history.
In August, a suicide bombing at a Quetta hospital claimed by the Islamic State group and a faction of the Pakistani Taliban killed 73 people.