The first European Games opened Friday in Azerbaijan's capital Baku with an extravagant opening ceremony featuring Lady Gaga.

During a two-hour ceremony at the 68,000-seat Olympic Stadium that celebrated the host nation's history and the importance of science, Azerbaijani President Ilham Aliyev declared the games open. Among those looking on were International Olympic Committee president Thomas Bach and many of the games' 6,000 athletes.

The multi-sport competition is an attempt to create a European equivalent to long-running events such as the Pan-American Games and Asian Games, but the build-up has been overshadowed by criticism of the ex-Soviet nation's jailing of political opponents. There are also concerns over the competition's sporting status, given that it will not host top-level athletics or swimming events.

Aliyev, who has ruled Azerbaijan since replacing his father Heydar in 2003, took a prominent role in the ceremony, entering the stadium bearing the European Games torch. His wife Mehriban, who heads the organizing committee, also gave a speech during proceedings.

"This spectacular celebration is the victory of independent Azerbaijan and each Azerbaijani citizen," she said. "Dear athletes, these games are for you."

The games are the brainchild of the European Olympic Committees and the organization's president Patrick Hickey.

"We are witnessing, we are creating a landmark moment in European sport," he said.

Hickey did not mention human rights, although he said "sport has a unique power to effect positive change" in society.

The ceremony featured an eclectic mix of themes, with Greek myth, a giant floating pomegranate and a video message from physicists at the Switzerland-based CERN research center all prominent. Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan were among the world leaders in attendance.

Lady Gaga's performance was kept a secret until part-way through the ceremony, with the American singer performing John Lennon's song "Imagine" while playing a piano covered in flowers. The singer, who wore a simple white smock as opposed to one of her signature eccentric outfits, was given a rapturous reception for her performance, which included an unusually full-throated rendition of the final verse of Lennon's low-key classic.

"I'm extremely honored to be playing at the opening ceremony in Baku, and to be celebrating all of the amazing athletes who will compete in the European Games in this beautiful city," she said in comments released by organizers.

Under pressure from human rights activists, Azerbaijan's government has demanded that politics and sport be kept separate during the games. However, politics intruded into the ceremony when the athletes from Armenia, Azerbaijan's traditional rival, were roundly booed by the crowd, who also shouted "Azerbaijan!"

Azerbaijan's Nagorno-Karabakh region and some adjacent territory have been under the control of Armenian soldiers and local Armenian forces since a 1994 cease-fire that ended a six-year war.

Other teams were warmly welcomed, with Azerbaijan's neighbor Turkey and fellow ex-Soviet states Ukraine and Russia receiving some of the loudest cheers - apart from the roar reserved for the host nation's team.

"I know I have made everybody - all my friends and family back home - really, really happy and I am honored myself," Olympic boxing champion Nicola Adams told The Associated Press earlier Friday as she prepared to be Britain's flagbearer at the ceremony. "It's an amazing opportunity and it is a once in a lifetime thing."

The ceremony saw athletes from Kosovo parade for the first time under their own flag at a major games, as one of the 50 nations which have sent athletes to compete across 20 sports.

Protests against Azerbaijan's human rights record took place in cities around the world Friday, although in Baku, where demonstrations are heavily restricted, opposition groups did not announce any protests ahead of the opening ceremony.

The day before, jailed journalist Khadija Ismayilova criticized Azerbaijan's government, writing that the country was in a "human rights crisis" and beset by high-level corruption.

"Things have never been worse," said Ismayilova's letter, released by the PEN organization, which said it had been smuggled out of prison in pieces.

The games run through June 28.