Nurdin Hasan, Banda Aceh – At least five people were injured when a grenade was thrown into a coffee shop owned by an Aceh Party leader in the city of Lhokseumawe, Aceh Province, on Wednesday evening, police officers and local residents said on Thursday.

"Two people riding a motorbike threw a grenade at the victims who were chatting and drinking coffee at the shop," Lhokseumawe district police chief Zulkifli said, adding that the police were still tracking down the culprits.

Experts have warned that tensions in the province surrounding the April 9 local and national legislative elections could deteriorate, potentially compromising Aceh's hard-won peace.

Police recently responded by dispatching additional Mobile Brigade officers there to help provide additional security.

The victims of Wednesday's attack were identified as Muhammad Raden, 32, who was rushed to the Lilawangsa Military Hospital in Lhokseumawe. Four others – Muhammad Amin Gadeng, 50, Asnawi, 30, Muhammad a.k.a Ombing, 37, and Syukri, 28 – were taken to the Kasih Ibu Hospital, also in Lhokseumawe.

Named Reintegrasi, or Reintegration, the coffee shop is owned by Efendi Sofyan, chairman of the Aceh Party's Panggoi branch. Muhammad a.k.a Ombing is local member of Aceh Transition Committee, or KPA, an organization set up to facilitate former Free Aceh Movement, or GAM, members' reintegration into society after the signing of the Helsinki agreement in 2005 to end the bloody struggle for independence by GAM members. The Aceh Party was founded by former GAM members.

An eyewitness identified as Razali said the victims were watching TV with their backs to the road in front of a wooden food stall at the time of the explosion. "I was at the corner of the shop when an explosion blasted out. I was very shocked because it happened so fast," he said.

Another witness said that rain and the speed of the incident prevent the people in the coffee shop from seeing the assailant. "I was drinking my coffee at that time when I heard an explosion and people were screaming because they were hurt by shrapnel from the explosion," he said.

The incident was the latest in a series of violent attacks ahead of the elections. In the past few months, Aceh Party offices and KPA members have been targeted in grenade attacks. And at least three Aceh Party and KPA members were shot dead in separate incidents last February. Police have so far failed to arrest the culprits.

Meanwhile, two businessmen, identified as Sofyan and Rusli, have been kidnapped by three armed men in Alue le Mirah village, said Rahman, a local resident speaking to journalists in Banda Aceh.

"They were measuring the land with some local residents when three armed men came and pointed their gun at them. The three people tied them up and took them into the forest," Rahman said.