Lebanese security officials say a grenade left behind from the 2007 fighting in a Palestinian refugee camp in northern Lebanon has exploded, wounding seven schoolchildren.

The officials say the children found the grenade on Wednesday and were playing with it when it exploded in the Nahr el-Bared refugee camp near the northern city of Tripoli.

One of the children was seriously hurt while the other six were lightly injured. The officials spoke on condition of anonymity in line with regulations.

The three-month battles in the Palestinian camp Nahr el-Bared between the Lebanese army and the al-Qaida-inspired group Fatah Islam caused massive destruction to the camp.

More than 170 soldiers died, as well as dozens of militants and Palestinian civilians.

About 400,000 Palestinian refugees live in Lebanon.