Police detained dozens of activists and petitioners in Beijing and elsewhere in China as US President Barack Obama arrived on his first state visit to the country, friends, family members and a human rights group said yesterday.

International rights groups have urged Obama to raise human rights concerns during a four-day trip to China that began on Sunday night and will include a meeting with Chinese President Hu Jintao (胡錦濤). China frequently conducts crackdowns on dissent ahead of major events, such as last year’s Olympics and this year’s National Day celebrations.