Heavily-armed militants killed eight soldiers in Indian Kashmir Monday in the deadliest such attack in five years, marring a landmark visit by Prime Minister Manmohan Singh to the embattled Himalayan territory.

The military convoy was ambushed on the outskirts of Srinagar, the main city of Indian-controlled Kashmir, as it headed towards a nearby base camp, officials said.

"Eight troopers died in the attack and 13 others have been wounded," a senior police official told AFP on condition of anonymity.

The condition of one of the injured was critical, he said.

The attack marked the deadliest single day for Indian security forces in Indian-controlled Kashmir since July 2008 when a landmine killed nine soldiers on a bus on the outskirts of Srinagar.

Monday's attack came amid a high state of alert which has been imposed ahead of Singh's arrival on Tuesday for a two-day visit to the territory, his first since June 2010.

Singh strongly condemned the attack in a statement issued in the capital New Delhi.

"This cowardly attack will not deter the security forces who are engaged in bringing peace and order to the Kashmir valley," he said.

Police sources said motorbike-borne militants opened fire at the army vehicles before lobbing a grenade at one of them.

As the militants fled they threw another hand grenade at a group of paramilitaries, severely injuring one officer.

They then abandoned their bike and escaped before the army cordoned off the area, the sources said.

Hizbul Mujahideen, a local pro-Pakistan militant group, claimed responsibility for the attack.

Security officials had earlier said that police and paramilitary forces were being deployed in strength across the region, with additional check points set up along major highways.

"A high alert is there. We do face a threat from the militants," Abdul Gani Mir, Kashmir's police chief, told AFP.

Kashmir, a picturesque Himalayan territory, is divided between India and Pakistan by a UN monitored de facto border known as the Line of Control (LoC) but it is claimed in full by both countries.

More than a dozen armed rebel groups have been fighting Indian forces since 1989 for the region's independence or its merger with Pakistan.

Tens of thousands of people, mostly civilians, have died in the fighting but armed violence has been in steady decline since the early 2000s.

Security concerns were raised on Saturday when armed rebels struck in a busy commercial area in the heart of Srinagar, the region's summer capital, killing two policemen in a shoot-and-run incident.

The three main separatist groups opposed to Indian rule have called for a mass strike for Tuesday to protest the visit of the prime minister.

"This is a protest against the forcible military occupation of Kashmir and we want to give the Indian prime minister this message that by hanging Afzal Guru, New Delhi has sent the entire Kashmiri people to the cross," Syed Ali Geelani, a top separatist leader, said in a statement.

Mohammad Afzal Guru, a Kashmiri Muslim, was secretly executed and buried inside a high security prison in New Delhi in February for his role in a deadly attack on India's parliament in 2001.

Four people were killed during a security crackdown against widespread protests over the hanging of Guru, who many people in Kashmir believe was framed.

Officials say a few dozen youths have been detained in police stations to "prevent protests" during Singh's visit, but separatist leaders put the figure in the hundreds.

Singh, who will be accompanied to Kashmir by the president of the ruling Congress party Sonia Gandhi, is scheduled to inaugurate a section of an ambitious railway project that is expected to link the land-locked Kashmir valley to the massive Indian rail network by 2018.

During a previous visit in 2009, Singh inaugurated another section of the project and also repledged a commitment to an economic reconstruction package worth $4 billion for the state.

However, experts and Indian political leaders have often said that New Delhi needs to extend a "political package" for dispute resolution.

"The Kashmir issue needs to be addressed politically. Economic packages are not a solution to the issue nor can it be found on the point of a gun," Kashmir's chief minister, Omar Abdullah, said recently.