A Saudi dissident living in Lebanon was killed in the Beirut suburbs and two of his brothers arrested in connection with the incident, Lebanese police and a security source said Monday.
The victim was stabbed to death on Saturday in his home in a southern Beirut area known to be under the security control of Hezbollah, a Shiite organisation backed by Saudi arch foe Iran.
His brothers confessed to killing him "for family reasons", a statement by Lebanon's Internal Security Forces said.
The police identified the man only by his initials, but a security source told AFP it was dissident Maneh al-Yami.
In a social media post on Sunday that did not name the victim, Waleed Bukhari, Riyadh's ambassador to Lebanon, expressed appreciation for the police's efforts to "uncover the facts and bring the perpetrators to justice".
Yami helped found in 2020 the National Assembly Party, a Saudi opposition party composed of dissidents exiled in Britain, the US and elsewhere.
He married his brother's ex-wife, and was killed in a fight over her right to take custody of her children, said a Lebanese security source, speaking on the condition of anonymity.
On Saturday Yami fought with his brother in support of his wife's custody demand. The brother then left Yami's house, and came back with their other brother to kill him, the source said.
The National Assembly Party said Sunday it was trying to pin down the exact circumstances of his killing including the "details and motives" of those involved.
It also said Yami had been in touch with the United Nations about trying to secure asylum in a different country. That could not be immediately confirmed on Monday.
Saudi Arabia is an absolute monarchy which does not tolerate any political opposition.
The National Assembly Party was the first organised political resistance during King Salman's rule. It's formation came during a growing state crackdown on dissent and freedom of expression in the kingdom.
According to the Lebanese police statement, Yami was born in 1980 and the two detained brothers in 1976 and 1990.
The police said the incident occurred at around 8:30 pm (1730 GMT) in Dahiyeh, a Hezbollah bastion.
The Lebanese security source said Yami had been living in Dahiyeh, which implies he was under at least tacit Hezbollah protection.
Saudi Arabia and Iran, the Middle East's two main power brokers, are waging a proxy war and jostling for dominance across the region, including in Lebanon.
Hezbollah has a military arsenal that rivals the state's and has also been the dominant force in Lebanon's parliament in recent years.
The organisation has been involved to varying degrees in conflicts in Syria, Iraq and Yemen, making it one of Tehran's most potent allies and an integral part of its foreign policy.