A bomb targeting a passenger train in southern Pakistan has killed at least five people and wounded more than 30, officials said, the latest in a series of attacks this year.

The explosion on Sunday near Unar station, in the Kashmor area of Sindh, badly damaged several carriages, according to the Agence France Presse news agency.

Security officials told Al Jazeera at least five were dead. A separate report by the Associated Press said as many as eight people, including three children, were killed.

Sardar Jamali, a senior local administration official, told AFP that the Khushhal Khan Khattak express was travelling to Peshawar from Karachi when it was hit by the blast

Three carriages were derailed and two of them were severely damaged by the force of the explosion. About 800m of track was damaged in the blast, he said.

The general manager of Pakistan Railways, Anjum Parvaiz, suggested it was a remote-controlled device planted on the track.

Sindh borders the restive province of Balochistan. Baloch separatists also operate in Sindh, although no one has claimed to have carried out the bombing.

A bomb in one of the compartments of a train on the same route on February 4 killed three people and wounded 20 in the central town of Rajanpur, in the Punjab.

Pakistan has endured a bloody start to the year with 114 people killed in attacks in January, according to an AFP tally.

On January 29 Nawaz Sharif, the prime minister, announced talks with the Pakistan Taliban to "give peace another chance", but some 60 more people have died in armed attacks since then.

The government says more than 40,000 people have been killed in violence since 2001, when Pakistan allied itself with the US's so-called "war on terror".