ISLAMABAD (AP) – A suicide bomber blew himself up inside a base housing paramilitary troops in the heart of the Pakistani capital on Saturday, killing eight troops and wounding several more, officials said.

The bomber sneaked into the base after dark from a wooded area at the rear and detonated his explosives inside one of several large tents used as sleeping quarters, senior police official Bin Yamin said.

Another four members of the paramilitary Frontier Constabulary, many of whose members are assigned to guard foreign embassies and VIPs in the city, were wounded, Yamin said.

The blast was the second in Islamabad in two weeks and follows a militant assault on a police academy in another major city that fueled fears for the stability of the nuclear-armed country.

A top Obama administration envoy is due in Islamabad this week to discuss Washington’s offer of more assistance, and call for more resolute action, to rout al-Qaida and the Taliban entrenched along the Afghan border.

A U.S. missile strike killed 13 people and a suicide car bomber hit an army checkpoint earlier Saturday in a frontier zone considered a militant redoubt. There was no claim of responsibility for Saturday’s attack on the police base. However, the leader of a Taliban faction accused of ties to al-Qaida warned Wednesday that militants would strike soon in Islamabad.

President Barack Obama has outlined a new strategy to turn around the faltering U.S. war effort in Afghanistan that pressures Pakistan to crack down on militants on its territory by making aid to the country conditional on its counterinsurgency efforts.

Pakistan insists it is committed to combating extremism, but U.S. officials have been critical of its attempts to reach peace deals with some militant groups and accuse Pakistan’s main intelligence agency of keeping questionable ties to some militant groups.