A Palestinian boy was killed and two people wounded in an Israeli military strike in southeast the Gaza Strip, medical sources and witnesses said Saturday.

The witnesses said that at least two shells landed on an open playground to the east of Khan Younis town, killing a six-year-old boy and hurting two of his companions.

An official at Abu Yousef al-Najjar hospital said the children were moderately wounded.

Violence resumed Friday as a ceasefire barely held for Thursday after three days of cross-border fire exchange. The Israeli aircraft carried out several strikes in the Gaza Strip late Friday and early Saturday, wounding 20 people.

Also on Friday, two Palestinian militants were killed in separate Israeli army strikes.

The Israeli attacks, started Monday, have killed 13 Palestinians so far, according to the Gaza health ministry.

The Palestinian militant groups said they fired rockets into Israel because it ignited this round of violence by killing two militants Monday.