By Zafar Abbas BBC correspondent in Islamic

The family members of American diplomats and non-essential staff at US missions in Pakistan are gradually moving out in wake of the grenade attack on a church in Islamabad earlier this month.

The US embassy in Islamabad says the process of moving out the diplomats' families and non-essential staff started this week and is still continuing.

Embassy officials say for security reasons they will not give details of the people who are being moved out.

Five people were killed in the attack - including the wife and daughter of an American diplomat.

No return

Embassy and airline sources say about 100 people have already left and many more are expected to move out in the next week.

It is believed that more than 250 people will be affected by the decision.

Ambassador Wendy Chamberlain: Accompanied children home

The American ambassador to Pakistan, Wendy Chamberlain, accompanied the group that was flown out in the first phase.

She has taken her two children with her to settle them in the US.

Although embassy officials say the ambassador will be back after consultations in Washington, the family members of the diplomats and most of the non-essential staff may not return to Islamabad in the foreseeable future.

This is the second time in six months that the US has moved its non-essential staff out of Pakistan.

It was first done following the American decision to start the military campaign in neighbouring Afghanistan.

Targets

However, most families and non-essential staff returned to Pakistan once things had started to settle down.

But following the grenade attack on a church this month, US officials believe militant groups linked to al-Qaeda may target more American citizens.

A US congressional delegation which met Pakistani President Pervez Musharraf during the week also raised the issue of security for American citizens.

But at the same time Washington has made it clear it will continue to support President Musharraf in his efforts to combat Islamic militancy in the country.