Kabul: Insurgents threw hand grenades into two homes in a Taliban provincial heartland Friday, killing a child and wounding six civilians in an area that has been at the center of the international coalition's push against the militants, a local Afghan official said.

Zhari, where Taliban leader Mullah Omar's radical Islamic movement was born just outside Kandahar city, was part of the focus of the US surge of 30,000 troops earlier this year.

US troops advanced on the district several months ago as part of a crucial strategy aimed at reducing violence in the nearby city by stemming the flow of fighters and weapons to the urban center.

US Homeland Security Secretary Janet Napolitano was in the Afghan capital Friday to speak with the Homeland Security officers working with the Afghan government to secure the country's porous borders from militants, as well as weapons and drug smugglers.

She was to spend New Year's Eve with US, troops and meet with Afghan and US officials in Kabul before heading to the Persian Gulf state of Qatar, the US Embassy said, but would not provide further details.

The United States, in an end-of-year review of its strategy in Afghanistan, has cited advances in its push against the Taliban in southern Afghanistan.

Yet the Obama administration, in the five-page section of the review released publicly in mid-December, acknowledged that while Taliban momentum has been stopped in some areas and reversed in others, "gains remain fragile and reversible."