Riyadh, KSA (BBN)- At least 10 people have been killed in a suicide bombing at a Shia mosque in Saudi Arabia's Eastern Province, a doctor has told the BBC.
The emergency doctor at Qatif Central Hospital said at least 70 had been injured, "some very critically".
Witnesses reported a huge blast at the Imam Ali mosque in the village of al-Qadeeh, in Qatif governorate.
It is the first such incident in Saudi Arabia amid rising tension in the wider region between Sunni and Shia Muslims.
It is unclear who was behind the attack.
Television pictures on Lebanon's al-Manar network showed shattered glass and debris next to the tiled pillars inside the mosque, where scores were said to have been praying.
Bodies covered in sheets could be seen laid out on the floor, while injured people in bloodstained clothes were rushed out on stretchers.
Qatif hospital has issued an urgent call for blood donations and called in off-duty staff to cope with the high number of casualties.
IS threat
Saudi Arabia's large Shia Muslim minority is mainly based in the Eastern Province, and there have been sporadic protests by Shia there for greater rights.
The attack on Friday comes at a time when the Saudis are leading a coalition of Arab states in an air campaign against Shia rebels in neighbouring Yemen.
Saudi Arabia has also been threatened by the Islamic State (IS) group, which is being targeted by a US-led coalition including the Sunni kingdom.
In November last year, an audio recording purported to be from IS chief Abu Bakr al-Baghdadi called on Saudi followers to attack Shia targets.
More than 2,000 Saudis are believed to have joined IS, with hundreds having returned home. Saudi Arabia has launched a security crackdown in recent months, arresting hundreds of IS suspects.
Al Jazeera's Hashem Ahelbarra, reporting from the capital Riyadh, said authorities expected the death toll the rise.
Saudi Arabia's Shia population is mostly based in two oasis districts of the Eastern Province - Qatif on the Gulf coast, and al-Ahsa, southwest of the provincial capital al-Khobar.
Qatif and al-Ahsa have historically been the focal point of anti-government demonstrations.
The kingdom's Shia community accounts for between 10 to 15 percent of the total population. They say they face discrimination in seeking educational opportunities or government employment and that they are referred to disparagingly in text books and by some Sunni officials and state-funded clerics.
They also complain of restrictions on setting up places of worship and marking Shia holidays, and say that Qatif and al-Ahsa receive less state funding than Sunni communities of equivalent size.
The Saudi government denies allegations of discrimination.