KHARKIV, April 7 - Two bomb attacks early Tuesday shook Kharkiv, Ukraine's second-largest city, causing some damage but no casualties in the government-controlled hub near the Russian border and the separatist-held east.

The Kharkiv prosecutor's office said a probe was underway for a "terrorist attack" after a loud explosion in the city center, which knocked out windows at a nearby university and set car alarms screeching, AFP reported.

The blast damaged a monument flying the national flag but failed to knock the flag off the pole, said a spokeswoman for the prosecutor's office.

In the past months the city of 1.4 million has been the scene of a string of bombings against military or strategic targets.

A Russian woman "suspected of organizing explosions", including the attack on the monument, was detained and homemade explosive devices as well as military equipment were found at her home, the Ukrainian security service said.

It described her as being an official of the self-proclaimed "Donetsk People's Republic" opposed to the Kiev government, "who was coordinating sabotage units in the Kharkiv region."

The second morning blast occurred on a railway line as a freight train was passing, damaging the tracks but causing no injuries or severe disruption to traffic, interior ministry officials said.

The early morning blasts came weeks after four people died when a bomb tore through a pro-government "Dignity March" marking the one-year overthrow of the former pro-Kremlin president, Viktor Yanukovych, on February 23.

Kharkiv is a major industrial center with a large university population and is the capital of an area bordering the pro-Russian separatist regions of Donetsk and Luhansk, where a year of fighting between insurgents and the army has left more than 6,000 people dead.

Kiev government officials say the attacks are orchestrated from Russia to destabilize a Russian-speaking region that harbors several aeronautical and aerospace firms as well as the Malyshev factories that manufacture tanks. (afp/ez)