Pakistan gunmen sketches issued

Police say they believe 10 people took part in the attack

Police in the Pakistani city of Karachi have released sketches of two men involved in an attack on a police station in which five officers died.

The authorities have also announced a reward of one million rupees (about $17,500) for information leading to the arrest of the attackers.

One of the gunmen was killed as police officers returned fire on Sunday, while at least nine others escaped by car.

The authorities believe that Islamic militants could be responsible.

Security tightened

Correspondents say suspicion for the attack has fallen on the militant Lashkar-e-Janghvi group, which has been involved in other violent attacks in Karachi.

A police official told the Associated Press news agency that investigators were looking into the possibility that an "ethnic-based political party" was involved, because its workers pelted the police station with stones a few days before Sunday's attack.

Security has been tightened at police stations across the city following the attack.

Police say that 10 attackers took part, and used a stolen car before walking into the station and opening fire on officers inside.

They have released sketches of two suspects. One man is clean shaven with spectacles and another has a thick crop of curly hair.

"Of course this is terrorism, but we don't know what kind yet," a police officer told AP.

Violent history

The city has seen several previous attacks by Islamist militants and has a history of Sunni-Shia Muslim sectarian violence.

Last month, police defused what they said was a huge car bomb outside the US consulate.

In 2002, attacks by Islamic militants on Western interests in the city killed nearly 30 people.

In the past few months, the government has intensified its campaign against banned militant groups, some of which are based in Karachi.