Parliament Speaker Ismail Kahraman says a bomb hit one corner of a public relations building inside the parliament complex, injuring some police officers.
He says there are no fatalities and that all legislators are safe at a parliamentary shelter.
Meanwhile in Istanbul, an official at the president's office says more than 50 military officers have been arrested in Istanbul and large crowds have carried out multiple citizen arrests.
Turkish TV channels are broadcasting scenes of soldiers being escorted away by policemen.
An official at Haydarpasa Numune Hospital in the Uskudar district of Istanbul tells The Associated Press they have admitted at least 150 wounded.
The official refused to comment whether there were fatalities. The official spoke on condition of anonymity because he wasn't authorized to speak to the media.
Earlier, NTV reported that six dead were brought to the same facility.