Oman's Sultan Qaboos, in Germany for medical treatment since July, said on Wednesday he would miss annual celebrations of his birthday this month in the sultanate he has ruled for more than four decades.

Many Omanis have been praying publicly for the safe return of their 73-year-old ruler after nearly four months abroad -- an unprecedented absence for the sultan.

Since taking power in 1970, Qaboos has transformed the small oil exporter from a poverty-stricken backwater torn by dissent into a prosperous Western-allied state, earning a reputation as a mediator seeking to ease periodic tensions between the Gulf states and neighbouring non-Arab Iran.

In a video message broadcast on state television, a frail-looking Qaboos offered greetings to Omanis on the occasion of his birthday, which falls on November 18 and is celebrated in Oman as a national day.

"The divine will has dictated that the occasion this year falls while we are outside the dear homeland for reasons you know," said Qaboos, seated on chair in a greenish-brown uniform and reading from a written text.

"But, by God's grace, He prepared the good results that will require a follow-up in accordance with the medical programme during the coming period," he added, without giving any further details.

Sultan Qaboos usually presides over an annual military parade in Muscat on his birthday, an event he is not known to have missed since ousting his father in a 1970 palace coup.

Oman's royal court last month told Omanis ahead of the Eid al-Adha holiday that Sultan Qaboos was in good health, but did not say what kind of tests he was undergoing or what he might be suffering from.

In his message, Sultan Qaboos also greeted Oman's armed forces, saying he remained committed to "equip them with whatever is necessary to carry out their duties and to deliver on their noble task of protecting the homeland and safeguarding its gains". - Reuters