Crown Prince Maha Vajiralongkorn has become Thailand's new king after accepting an invitation from parliament to succeed his father, King Bhumibol Adulyadej, who died in October.
The new monarch, 64, who received the title "His Majesty King Maha Vajiralongkorn Bodindradebayavarangkun", assumed his new position on Thursday, according to an announcement broadcast on all TV channels.
He ascends the throne 50 days after the death of his father, who reigned for 70 years.
"I agree to accept the wishes of the late king... for the benefit of the entire Thai people," he said. "This royal succession highlights a desire for stability and continuity in Thailand,"
Vajiralongkorn addressed his audience, which included Royal Regent Prem Tinsulanonda and Prime Minister Prayut Chan-ocha, before holding a private meeting with the regent and key government figures.
The prince has not spoken publicly since his father's death and news about his plans has come through the government.
Vajiralongkorn, the only son of King Bhumibol who is also known as King Rama IX, did not immediately ascend the throne following his father's death as traditionally practised, instead requesting more time to mourn.
Al Jazeera's Wayne Hay, reporting from Bangkok, said the announcement was delayed by a couple of hours and the footage broadcast on television was pre-recorded.
"It is a historic day ... a new king," he said.
"But Thailand is still in mourning for the passing of the late king 50 days ago so there will be mixed emotions for many Thais. But there will also be celebration of the announcement."
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Earlier on Thursday, Channel News Asia reported that the crown prince had arrived for the ceremony from Germany, where he has a home.
Thursday's religious ceremony will continue into Friday, with Vajiralongkorn presiding over the rites on both days. The Grand Palace is closed for both mourners and tourists on both days.
News about the royal succession, and criticism about the crown prince, have been muted.
