Four soldiers were killed and seven were wounded Monday in an attack by suspected rebels on an army convoy in Indian-controlled on the eve of a visit by Prime Minister Manmohan Singh.

The attack comes even though government forces intensified their patrols ahead of Singh's visit to prevent protests and attacks by rebels fighting against Indian rule.

Singh's two-day visit starting Tuesday also follows a weekend attack in which militants shot and killed two policemen in Kashmir's main city of Srinagar.

Police detained scores of separatist activists, frisked residents and searched cars as part of security measures.

"We're taking all possible security measures to have an incident free visit by the prime minister," said Ashok Prasad, director general of police.

But Col. Brijesh Pandey, an army spokesman, said that suspected rebels fired at an army convoy on a highway on the outskirts of Srinagar late Monday, killing the four soldiers and wounding the others.

In a second attack further along the same highway, militants lobbed a grenade at security forces, critically wounding a paramilitary officer, a police official said.

Police and paramilitary troops have launched a search operation in the area, Pandey said.

Singh will inaugurate part of a rail line that connects southern and northern Kashmir, and meet officials to review development projects.

Separatists have called for a strike on Tuesday, saying the Kashmir dispute cannot be resolved by economic grants and developing rail services.

"It is highly unfortunate that India has treated this issue as a simple problem of administration and economics," said Mirwaiz Umar Farooq, a separatist leader who has been placed under house arrest

Muslim-majority Kashmir, divided between India and Pakistan, has long demanded either independence from India or a merger with neighboring Pakistan. Since 1989, an armed rebellion and subsequent Indian crackdown in Indian-held Kashmir have claimed at least 68,000 lives.

Singh's visit comes amid calls from pro-India Kashmiri groups for starting a peace process with all the stakeholders, including separatists and Pakistan.

Experts say Singh could use his visit to convey a message of dialogue to Pakistan's newly elected leadership, as well as to Kashmiri separatists.

"It's more a symbolic gesture that every visiting prime minister offers reconciliation and dialogue to Pakistan from Kashmiri soil. So we expect the same again," said Sheikh Showkat Hussain, a law professor.

When Singh last visited Kashmir three years ago, huge streets protests erupted as the separatists rejected his offer of talks.

Separately, at least 112 people were killed that summer as troops fired live ammunition into protesting crowds, inciting further protests in a deadly cycle of violence that ended only when winter blanketed the Himalayan region.

Since then, the authorities have stepped up developmental projects. There has been a greater push to promote tourism, increase public infrastructure such as healthcare facilities, and strengthen pro-India political activities.

Simultaneously, officials have exercised strict control over separatists' activities, mostly barring them from conducting public meetings, confining leaders to their homes, arresting and later releasing thousands of Kashmiri activists.