KATHMANDU (Reuters) - A summit of South Asian leaders set for Islamabad in November may be called off as several countries have decided not to attend amid rising tension between arch-rivals India and Pakistan, officials said on Wednesday.

Afghanistan, Bangladesh, Bhutan and India have expressed their "inability" to attend the summit of the South Asian Association for Regional Cooperation (SAARC), a senior foreign ministry official in Nepal said.

India's foreign ministry on Tuesday announced its decision to skip the meeting, saying "increasing cross-border terrorist attacks in the region and growing interference in the internal affairs of member states by one country" had created an environment that was not conducive.

India has blamed Pakistan for a deadly assault this month on an army base in the disputed Himalayan state of Kashmir that has heightened fears of a new conflict between the nuclear-armed neighbors.

Pakistan, which denies the accusations, called India's move to pull out of the SAARC summit "unfortunate".

A spokesman for Afghan President Ashraf Ghani said Afghanistan, which frequently accuses Pakistan of harboring and supporting Taliban insurgents, would not take part in the summit as long as security threats in the region remain unresolved.

A Bangladeshi foreign ministry official said Dhaka had told Nepal it would not attend because of Pakistani interference in its internal affairs.

The two countries have been in a diplomatic spat over executions by Bangladesh of people convicted of crimes during its 1971 war of independence from Pakistan.

Junior foreign affairs minister Mohammad Shahriar Alam said Dhaka had told Pakistan, which is chairing the meeting, of its "inability to attend the summit due to our engagements".

Rishi Adhikari, the foreign affairs adviser to Nepal's prime minister, said the Himalayan nation's government would discuss the matter with SAARC members so that there was "no long-term effect" on the regional grouping.

(Reporting by Gopal Sharma in Kathmandu; Additional reporting by Serajul Quadir in Dhaka and Hamid Shalizi in Kabul; Writing by Aditya Kalra; Editing by Paritosh Bansal and Clarence Fernandez/Mark Heinrich)