* Xi says Hong Kong, Macau affairs internal
* Macau's patriotism key for city's success - Xi
* Xi's visit expected to kick start economic diversification
* Security clampdown, ferry and train services curtailed (Adds details of new China-Macau economic measures)
By Joyce Zhou
MACAU, Dec 20 (Reuters) - President Xi Jinping said on Friday China would never allow foreign forces to interfere in its special regions, including Hong Kong, as he swore in a new pro-Beijing government for the gambling hub of Macau.
At a ceremony marking the 20th anniversary of Macau's handover to Chinese rule, Xi heaped praise on the former Portuguese colony for its patriotism and loyalty, but did not refer directly to six months of anti-government protests in the former British colony of Hong Kong.
"I must emphasize, since Hong Kong and Macau’s return to the motherland, dealing with these two Special Administrative Regions' affairs is entirely China's internal affairs and none of the business of foreign forces,” Xi said.
"We do not let any external forces interfere.”
Macau returned to Chinese rule on Dec. 20, 1999, with the same "one country, two systems" formula aimed at ensuring a high degree of autonomy under which Hong Kong is governed.
While protesters in Hong Kong, across the mouth of the Pearl River, are furious about what they see as Beijing's erosion of their freedoms, Macau has seen little dissent.
Beijing denies undermining Hong Kong's autonomy and has repeatedly blamed foreign governments, including the United States and Britain, for stirring up trouble in the financial hub.
Xi swore in new Macau chief executive Ho Iat-seng and his administration, which will run the enclave of several islands for the next five years.
Under a large Chinese flag and a smaller Macau one, Xi shook hands with Ho, who was selected in August by a largely pro-Beijing committee in a similar process to the way Hong Kong's leader is chosen.
Xi made no reference to Macau's casino industry, which accounts for more than 80% of its revenues, but encouraged diversification and urged it to grasp opportunities brought by a regional development zone known as the Greater Bay Area.
He also stressed further integration with the mainland, although he did not announce any specific steps.
Officials and corporate executives have been expecting Beijing to reward Macau for its loyalty with measures including a new yuan-denominated stock exchange.
Xi said Macau's patriotism was "the most important reason" for the success of its "one country, two systems formula of governance". He said China would be unwavering in the defence of its sovereignty.
"The will of the Chinese government and the Chinese people to safeguard national sovereignty, security and interest in development is rock solid," Xi said.
"The forward steps of the Chinese nation's rejuvenation are unstoppable."
Xi said he was pleased Macau had implemented national security legislation, unlike Hong Kong which has yet to do so because of widespread opposition.
Residents of Macau enjoyed "law-based rights, freedoms" in one of the world's safest cities where people "rationally" expressed different views, he said.
Macau has been decked out for the anniversary with flags and red banners over schools, offices and along roads.
Security and border controls have been on lockdown for Xi's three-day visit, which ends on Friday, to prevent any spillover of dissent from Hong Kong.
Journalists, activists and even the heads of the American Chamber of Commerce in Hong Kong were barred from entering the city in the run-up to the visit. Macau authorities have not commented on the issue.
More than half of Macau’s population of 620,000 immigrated from China in recent decades which has helped foster more affinity for the mainland than in Hong Kong, where most people were born in the territory.
China's banking and insurance regulator announced measures to further strengthen financial cooperation between Macau and China soon after Xi left. These include supporting Macau banks to set up institutions in the mainland and mainland insurance funds to invest in Macau, the regulator said in a statement.
Millions of dollars have been spent on Chinese government-linked youth associations that encourage study on the mainland.
Xi said he hoped Macau would establish more patriotic associations to "perfect" governance and ensure stability and prosperity. (Reporting by Noah Sin, Donny Kwok, Clare Jim, James Pomfret in Hong Kong Writing by Farah Master; Editing by Janet Lawrence )