The images from Mumbai, India – crumbled railway cars, blood-spattered victims – were hauntingly familiar. Although the results are as horrific and despicable, this terrorist attack, unlike the ones on trains and buses in London and Madrid, is complicated by the motives of the apparent perpetrators.

Media reports say that militants opposed to Indian control of the Kashmir state are likely responsible for Tuesday’s evening blasts that killed 190 people. If true, this could stall or derail talks between India and Pakistan on the future of the Kashmir issue. With another round of talks scheduled for next week, this can’t be allowed to happen.

Bombs exploded on at least seven trains within minutes during the evening rush hour in Mumbai, India’s financial capital. All the blasts were in first-class cars, indicating that India’s professional class was targeted. More than 600 people were injured.

Although Indian officials said they do not yet know what groups were involved, suspicion quickly turned to Lashkar-e-Taiba, a group based in Pakistani-controlled Kashmir that seeks to end Indian control the region in the Himalayan mountains claimed by both India and Pakistan. Also on Tuesday, grenade explosions in Srinagar, the summer capital of Indian-administered Kashmir, killed eight.

In 2001, Kashmiri militants attacked the Indian Parliament and killed nine people. India blamed Lashkar-e-Taiba and mobilized troops along its border with Pakistan and Pakistan responded in kind. Both countries have nuclear weapons.

With international persuasion, the countries began negotiations, which are on-going. The discussions have also led to an easing of restrictions on travel between Pakistan and Indian and through Kashmir. For the first time in more than 50 years, buses are now crossing the Line of Control that splits Kashmir to travel between the two countries.

Tuesday’s attacks raise the question of how much violence and killing India is willing to tolerate to improve relations with Pakistan, says Xenia Dormandy of the Belfer Center for Science and International Affairs at Harvard’s Kennedy School of Government.

“How long can India, Indians and the Singh government withstand the constant pressure from militant groups before they have to react?” she wrote in Wednesday’s Washington Post, adding that Pakistan must do more to shut down militant groups that operate from its territory. “By any measure of international diplomacy, they’ve been extraordinarily patient.”

That patience will be tested in coming days as more details of Tuesday’s attacks emerge. But, with backing from the United States and other countries, India and Pakistan must continue their dialogue.