Members of Saudi Arabia's Shiite minority refuse to be provoked by the bombing, say 'they just want justice' for the death of 21 people
Saudi Arabia's King Salman pledged on Sunday that anyone linked to the killing of 21 minority Shiites will face justice for the "heinous crime".
Salman made the vow in a telegram to Crown Prince Mohammed bin Nayef, who is also the interior minister.
"Anyone taking part, planning, supporting, cooperating or sympathising with this heinous crime will be held accountable, and will be subject to legal accountability. He will receive the deserved punishment," the king said in the message carried by the official Saudi Press Agency.
More than 100 people were also wounded when a Saudi suicide bomber detonated explosives inside a mosque in the Shiite majority Qatif district of Eastern Province on Friday.
The king said "we were... pained by the intensity of this terrorist crime that contradicts the values of Islam and humanity" and which targeted innocent civilians.
The interior ministry said the suicide bomber belonged to a cell of which 26 members have been arrested, confirming his identity and said he had links with the Islamic State (IS) group.
In a statement carried by the official Saudi Press Agency late on Saturday, the interior ministry identified the bomber as Salih bin Abdulrahman Salih al-Ghishaami, a Saudi national.
"He was wanted by security services for belonging to a terrorist cell receiving directions from Daesh abroad," the ministry said.
It was the deadliest attack in years to strike the kingdom, and marked the first time IS had claimed an attack in Saudi Arabia.
No retaliation, 'they just want justice'
Members of Saudi Arabia's Shiite minority refused to be provoked by the bombing that authorities called an attempt to promote sectarian strife.
"No, no, no... There is no action" in the form of retaliation, a Shiite resident who said he lost three friends in the attack in Kudeih village told AFP on Sunday.
"They just want justice."
Naseema Assada, a resident of Qatif city near the stricken village, said she visited seven families whose loved ones died in the bombing.
"They are angry at Daesh and radical Sunnis," but not at Sunnis in general, she said, using an Arabic acronym for IS.
Residents said two children were among the dead, and plans were being made for a mass burial.
Demonstrators took to the streets of the region on Saturday to denounce the attack, which residents said occurred despite security checkpoints in Qatif.
"This is strange," Assada said. "The government should protect people and if it's not, this is the government's fault."
It is the second mass killing of Shiites in the kingdom since late last year.
In November, gunmen killed seven Shiites in the Eastern Province town of Al-Dalwa. Authorities said the suspects were linked to IS.
Although militants attacked Westerners and government targets in Saudi Arabia between 2003 and 2007, the Al-Dalwa shootings were the first major assault against Shiites.
'Some imams spewed hatred'
Saudi Arabia and its Gulf neighbours last year joined a US-led military coalition bombing IS in Syria, raising concerns about possible retaliation in the kingdom.
Since late March, Saudi Arabia has also led a coalition bombing the Shiite Houthi militia which has seized large parts of Yemen. In retaliation for the bombing campaign the Houthi have sent deadly shell fire into Saudi Arabia.
Political and religious leaders in the kingdom, and its media, were unanimous in denouncing the mosque bombing.
The interior ministry said the attack against "honourable citizens was carried out by tools controlled by foreign forces that aim to divide the unity of society and pull it into sectarian strife".
Saudi Arabia's top cleric, Grand Mufti Sheikh Abdul Aziz al-Sheikh, called it a "criminal act" which targeted national unity.
But columnist Khaled Almaeena, writing in Sunday's Saudi Gazette, complained that "some imams spewed hatred and spread falsehood about Muslims of other sects.... we should not have remained silent".
The Qatif attack occurred despite the arrest since December of nearly 100 suspected militants, most of them allegedly linked to IS.