MOSCOW, May 15 (Xinhua) -- A Moscow court on Tuesday sentenced Russian opposition leader Alexey Navalny to 30 days in custody for organizing unauthorized rallies in Russian cities on May 5 and offering resistance during his detention.

"They have announced the verdict of 30 days and the trial still continues. They are preparing another sentence," Navalny said in his Twitter account.

He was reportedly subject to the sentence for repeatedly violating established rules of organizing public events.

In addition, the Moscow City Court later sentenced Navalny to administrative arrest of 15 days for offering resistance to the police during his detention at the rally, Interfax news agency reported.

Nevertheless, the court specified that the two terms of arrest Navalny was sentenced to do not add up and they both started on Tuesday, which means he will remain in custody for a total of 30 days.

The opposition leader said on Twitter that he would continue to go out to the streets and express his opinions "as many times as necessary."

Navalny was detained during a rally in central Moscow two days before the inauguration of Vladimir Putin as Russian president, but was later released pending trial.

Around 300 people were detained along with Navalny during that rally and another 200 were detained in St. Petersburg during another rally held by his supporters, according to local police departments.

Russian media reported that the number of people detained during rallies in Russian cities on the eve of the inauguration reached up to 1,000.