An explosive device detonated on a beach in the Black Sea resort of Sochi on Thursday, killing two and injuring as many as 13, authorities said.

President Dmitry Medvedev quickly ordered his envoy to the Southern Federal District, Vladimir Ustinov, to oversee the investigation of the explosion, the second deadly blast in the last five weeks in Sochi, which is to host the 2014 Winter Olympics.

German Chancellor Angela Merkel is scheduled to meet with Medvedev in Sochi on Aug. 15.

The device exploded on a beach in the village of Loo, just north of Sochi, at around 10:30 a.m. Thursday, Investigative Committee spokesman Vladimir Markin said in a statement. Killed in the blast were a 31-year-old man and a 22-year-old woman, while four others were hospitalized with injuries, Markin said.

In a statement posted on their web site, Sochi police identified the dead woman as a resident of Kiev and the dead man as a resident of Rostov-on-Don. Eyewitnesses told Interfax that the bomb was hidden in a bag lying on the road that the woman tried to pick up.

The blast could be heard a kilometer away, witnesses told Interfax.

An unidentified regional police source told Interfax that at least 13 people were injured in the explosion — including an 8-year-old girl — five of whom were hospitalized. Most of the victims were residents of the Rostov region and the Sverdlovsk region city of Nizhny Tagil, the source said.

Krasnodar Governor Alexander Tkachyov, who arrived at the scene, said the bomb could have been deliberately planted, Interfax reported, though he gave no possible motive. Tkachyov promised financial compensation to all of the victims, Interfax said.

Krasnodar regional prosecutors have opened a criminal case on charges of multiple homicides, which carry a punishment of up to life in prison, Markin said in the statement.

Sochi police announced a reward of 2 million rubles ($84,800) for any information that would help lead to the perpetrators, Interfax reported.

A device exploded in an apartment building in Sochi on July 2, killing two people and injuring more than 30. In a sign of how seriously the Kremlin took the July 2 blast, a team of experts from Moscow was flown down to Sochi to handle the investigation.

Moscow lobbied extensively to host the 2014 Olympics, even sending then-President Vladimir Putin to make a personal pitch to the selections committee. Russia has portrayed its selection as a sign of its prestige, symbolizing an increase of its presence and influence on the international stage.