Rulers of the Arab states of the Gulf, where ageing monarchs retain power, congratulated Qatar's new young emir Sheikh Tamim bin Hamad al-Thani, whose father abdicated in his favour on Tuesday.
At the age of 33, Sheikh Tamim becomes the youngest ever sovereign in the Gulf Arab monarchies.
His father Sheikh Hamad, 61, suffers from kidney problems but officials insist his reasons for stepping down were not health-related but rather a determination to bring a younger leadership to the fore.
The first reaction came from Saudi Arabia's 90-year-old King Abdullah. He congratulated Sheikh Tamim, who has played a major role in improving relations between Qatar and the regional powerhouse, which had been strained until 2007 over a border dispute.
"We are happy to express to you in the name of the people and Saudi Arabia's government and in our name, our sincerest congratulations," King Abdullah said in a statement published by SPA.
"We are confident that you will continue the journey of your father... and his efforts in serving the state of Qatar and its brotherly people as well as strengthening relations between the two nations."
King Abdullah's age and frequent hospitalisation have raised concerns about the future leadership of his ultra-conservative kingdom, a key player in the Middle East and a major exporter of oil.
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Recently, the king had carried out a series of reshuffles of princes holding government posts in the OPEC kingpin.
The United Arab Emirates also congratulated Sheikh Tamim, voicing hope of stronger ties, the official WAM news agency reported.
UAE President Sheikh Khalifa bin Zayed al-Nahayan affirmed "the deepness of the brotherly relations between the two countries and the keenness to strengthen them to serve the people of both states," WAM said.
Relations have become strained during the past few months over Qatar's reported support of the Muslim Brotherhood, which, allegedly backed by the gas-rich state, has risen to power in several Arab Spring states.
Dozens of people are on trial in the UAE over their suspected links to the Islamist movement, with 94 of them accused of forming a "secret organisation plotting to overthrow the regime."
Kuwait's emir, Sheikh Sabah al-Ahmad al-Sabah, was the first leader to meet Tamim as he headed to the gas-rich state to offer the new emir his best wishes, the official KUNA agency said.
Congratulations also came from Oman, where Sultan Qaboos has been in power for four decades, and Bahrain's King Hamad, whose country has been rocked by a Shiite-led uprising demanding the ouster of the prime minister, the monarch's uncle, since February 2011.
Sheikh Hamad's abdication is a rarity in the Arab world, where autocratic rulers held power uncontested for decades until the Arab Spring revolutions that toppled regimes in Tunisia, Egypt and Libya.