* First mass rally in Ukraine in 2014 draws at least 50,000 people
* Opposition calls for Western sanctions against government officials
* U.S. Senate's Foreign Committee to hold hearing on Ukraine on Jan.15
KIEV, Jan 12 (Reuters) - At least 50,000 opponents of Ukraine's President Viktor Yanukovich rallied in a central Kiev square on Sunday, reviving the protest movement after a Christmas and New Year lull.
The mass rally in Independence Square was a continuation of street protests that erupted in November following Yanukovich's decision to abandon a free trade agreement with Europe in favour of closer cooperation with Russia.
Sunday's demonstration came a day after baton-wielding riot police tried to disperse protesters outside a Kiev courthouse, sparking clashes in which at least ten people were injured.
"What are the next steps? We will fight... protest peacefully," Vitaly Klitschko, an opposition leader and former heavyweight boxing champion, told the crowd which waved the blue-and-yellow national flags of Ukraine.
"Today the authorities use the militia as a weapon, silencing the people's mouths with batons," he said, and repeated the opposition's call for early presidential elections.
Unless the vote is brought forward, a presidential race is not due until 2015.
Another opposition leader, Arseny Yatsenyuk, called on the West to impose sanctions against senior state officials, including Interior Minister Vitaly Zakharchenko, who, he said, had violated Ukraine's constitution by authorising the use of force against the protesters.
The U.S. Senate Committee on Foreign Relations is due to hold a hearing on Ukraine on Jan. 15, according to the committee's website.
In November, Yanukovich's government walked away at the last minute from a deal tying Ukraine closer to the European Union and opted for closer ties with Kiev's Soviet-era overlord Moscow.
The decision prompted street demonstrations opposing the decision and the movement quickly developed into an all-out protest against Yanukovich and his government.
The protest rallies attracted as many as 800,000 people at their height but the movement quietened over New Year and the Ukrainian Orthodox Christmas, which was celebrated on Jan.7. (Reporting by Pavel Polityuk and Natalia Zinets, writing by Gabriela Baczynska, editing by Rosalind Russell)