Belarus police carried out mass arrests as tens of thousands of people again gathered for protests calling on leader Alexander Lukashenko to step down. More than 50 people were detained on Sunday, rights groups said. Video footage appeared to show police spraying an irritant directly into the faces of protesters in one city. It was the 50th day of protests following August's disputed presidential vote. Earlier this week Mr Lukashenko held a secret inauguration. The electoral commission says Mr Lukashenko won a sixth term with more than 80% of votes. But the opposition says he cheated and that they won the election with at least 60% of the vote. Several EU countries and the US say they do not recognise Mr Lukashenko as the legitimate president of Belarus. Police admitted using tear gas and stun grenades to disperse what they called "disobedient" protesters in the eastern city of Gomel on Sunday. But local media footage circulating online showed officers spraying a substance directly into people's faces. Many of the protesters were women, who retreated while shouting "fascists". Meanwhile in the capital Minsk, where tens of thousands of people gathered for the seventh straight weekend of protests, riot police pulled people out of crowds and hauled them away in vans, a Reuters news agency witness said. Mr Lukashenko was quietly inaugurated on Wednesday morning, without any of the usual pre-publicity and fanfare.