The demonstrators also blocked traffic and disrupted work in government offices.
Tuesday is the second day of the Samajwadi Party's three-day campaign targeted at Mayawati's Bahujan Samaj Party (BSP) government.
Several Samajwadi leaders, including Azam Khan, were detained in Rampur district. A large number of party activists were attacked with batons by police in Basti district.
Shouting anti-government slogans, the activists barged into government offices in Gorakhpur district. In the same district, they also blocked a train.
'We will continue with our campaign irrespective of the harsh measures adopted by the Mayawati government against us,' party spokesman Rajendra Chaudhary told reporters here.
According to reports, Varanasi, Allahabad, Kanpur and several other major cities too witnessed similar demonstrations.