Turkish Airlines (http://www.thy.com/en-INT/) offers daily domestic flights from Istanbul IST and Ankara to Diyarbakir DIY.
There are trains three times a week from Istanbul Güney Express via Ankara and a number of other cities on the way, including Kayseri, Sivas, and Malatya among others. There is also another daily train from Ankara 4 Eylül Mavi Treni, which takes the same route with Güney Express. On its way back to Istanbul, Güney Express, which comes from Kurtalan and Batman about 2 hours further east from Diyarbakır, departs from Diyarbakır on Mondays, Wednesdays, and Fridays around noon. Trains to Istanbul get really overcrowded during early August because of huge numbers of seasonal workers taking the train to get to hazelnut orchards around Adapazarı and Eastern Marmara on the way short of two hours from Istanbul—the last stop of the trains, and it is impossible to find a ticket during that season without booking/buying the ticket in advance. Even if you can find a ticket, the ride is very uncomfortable, and because of the huge numbers of passengers getting off the train in almost each stop—even if it is in the middle of nowhere, where normally no one ever gets on or off—to replenish their water from station fountains, trains are extremely delayed, and it takes almost two full days to get to Istanbul. Avoid if you are not deadly on budget.
Many local bus companies offer services from cities all over Turkey. The bus from Erzurum takes 6 hrs from 50TL tourist price to 35TL. The main bus station otogar is about 10 km away from city centre, along the highway to Urfa.
When traveling from Diyarbakir to west by bus be prepared for several ID check ups at military checkpoints.
