(Adds Indian prime minister's letter)

NEW DELHI, Oct 19 (Reuters) - India condemned Friday's bomb attacks on former Pakistan Prime Minister Benazir Bhutto as reprehensible and urged Islamabad to do more to curb "terrorism" in the region.

More than 130 people were killed in the twin blasts -- blamed on Islamist militants -- aimed at Bhutto as she was driven through Karachi to greet supporters on her return from eight years in exile.

"We strongly condemn the terrorist attack in Karachi," Indian Foreign Ministry spokesman Navtej Sarna said. "It is reprehensible that senior political figures are targeted in this way with such loss of innocent life.

"The spectre of terrorism confronting our region requires strong and determined action by all our governments," he said in a statement.

Indian Prime Minister Manmohan Singh was sending a letter to Pakistan President Pervez Musharraf "expressing his deep concern on the dastardly act in Karachi", Sarna said in another statement later on Friday.

Singh and his Foreign Minister Pranab Mukherjee had also conveyed their "personal concerns and sympathies" to Bhutto and she had thanked them and the people of India for their concern and prayers, he said.

The attack on Bhutto came as the nuclear-armed neighbours began a new series of peace talks on Thursday as part of a larger peace process they launched in 2003/04 after coming close to the brink of war.

The two sides discussed conventional security issues on Thursday, reviewed nuclear security measures on Friday and will hold the second meeting of a joint counter-terrorism panel on Monday.

While the dialogue has reduced tensions, it has lost momentum over the key Kashmir dispute, and with both governments hemmed in by domestic politics, few analysts expect a breakthrough in the near future.

New Delhi also continues to point fingers at Pakistan-based Islamist militant groups and Pakistan's military spy agency for frequent bomb attacks in India even though it has not been able to produce much in terms of hard evidence.

India also says that rising militant attacks within Pakistan showed how Islamist groups there were turning against their own masters, who it says aided such outfits in the past.

On Thursday, Singh said the peace process had slowed down due to Pakistan's internal troubles, the Indian Express newspaper quoted him as telling reporters on his plane on the way back from a visit to Africa. Asked if the return of Bhutto, who is expected to lead her party in national polls, would speed the process, Singh said: "The new political order in Pakistan is yet to take shape."

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